# Association between in utero exposure to acetaminophen and external genital tract malformations in boys and girls: a systematic review and meta-analysis

Lina Eletri, Kristen Joseph-Delaffon, Agnes Dechartres, Per Damkier, Jonathan Richardson, Elisabeth Elefant, Delphine Mitanchez, Benoit Marin

<figure><img src="image_1.png" /></figure>

## To cite this version:

Lina Eletri, Kristen Joseph-Delaffon, Agnes Dechartres, Per Damkier, Jonathan Richardson, et al. Association between in utero exposure to acetaminophen and external genital tract malformations in boys and girls: a systematic review and meta-analysis. Human Reproduction, 2026, pp.deaf253. 10.1093/humrep/deaf253. hal-05520643

HAL Id: hal-05520643

https://hal.sorbonne-universite.fr/hal-05520643v1

Submitted on 20 Feb 2026

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons CC BY 4.0 - Attribution - International License
1 Association between *in utero* exposure to acetaminophen and

2 external genital tract malformations in boys and girls: a systematic

3 review and meta-analysis.

4 Running title: Acetaminophen exposure and genital malformations

5

6 Authors: Lina Eletri¹,², Kristen Joseph-Delaffon³, Agnes Dechartres⁴, Per Damkier⁵,⁶,

7 Jonathan Richardson⁷, Elisabeth Elefant⁸, Delphine Mitanchez³,⁹,†,* and Benoit

8 Marin¹,†,*

9 ¹Sorbonne Université, INSERM, Institut Pierre Louis d'Epidémiologie et de Santé

10 Publique, Equipe PEPITES, AP-HP, Hôpital Pitié Salpétrière, Département de Santé

11 Publique, Centre de Référence sur les Agents Tératogènes (CRAT), F75013, Paris,

12 France.

13 ²Department of Neonatology, Centre Hospitalier du Mans, Le Mans 72037, France.

14 ³Department of Neonatology, Bretonneau Hospital, François Rabelais University, F-

15 37000 Tours, France.
16 $^4$Sorbonne Université, INSERM, Institut Pierre Louis d'Epidémiologie et de Santé

17 Publique, Equipe PEPITES, AP-HP, Hôpital Pitié Salpêtrière, Département de Santé

18 Publique, AP-HP, 75013 Paris, France.

19 $^5$Department of Clinical Pharmacology. Odense University Hospital, Odense,

20 Denmark

21 $^6$Department of Clinical Research University of Southern Denmark, Odense,

22 Denmark

23 $^7$UK Teratology Information Service. Newcastle-upon-Tyne Hospitals NHS

24 Foundation Trust and UK Health Security Agency, United Kingdom.

25 $^8$AP-HP. Sorbonne Université, Hôpital Trousseau, Département de Santé Publique,

26 Centre de Référence sur les Agents Tératogènes (CRAT), F75012, Paris, France.

27 $^9$INSERM UMRS_938 Centre de Recherche Saint Antoine, F-75012 Paris, France.

28 †Both authors contributed equally

29 *Correspondence address: Benoit Marin, Hôpital La Pitié Salpêtrière, Bâtiment

30 Mazarin, 47-83 Bd de l'Hôpital, 75013 Paris, France Delphine Mitanchez. Email

31 benoit.marin@aphp.fr ORCID Id 0000-0001-8857-0910 or Delphine Mitanchez, 2 Bd
32 Tonnellé, 37000 Tours, France. Email: delphine.mitanchez@univ-tours.fr ORCID Id

33 0000-0001-8787-6846.
34 Abstract

35 **Study question:** Is the use of acetaminophen during pregnancy associated with
36 external genital tract malformations in boys and girls?

37

38 **Summary answer:** This meta-analysis found no evidence linking *in utero*
39 acetaminophen exposure to external genital malformations in boys but further
40 research focusing on girls and considering relevant confounding factors is needed.

41 **What is known already:** Acetaminophen is widely used by pregnant women, but
42 findings are conflicting regarding a possible increased risk of genital malformations in
43 the offspring of both sexes.

44 **Study design, size, duration:** In this systematic review and meta-analysis, we
45 searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials,
46 International Clinical Trials Registry Platform, ClinicalTrials.gov on April 18, 2024, and
47 subsequently updated the search on September 20, 2025 for randomized controlled
48 trials and observational studies. This meta-analysis included randomized controlled
49 trials and observational studies focusing on the association between *in utero* exposure
50 to acetaminophen, with no restriction on publication dates and languages.

51 **Participants/materials, setting, methods:** Two reviewers independently screened
52 studies, extracted data and assessed risk of bias. The two primary outcomes were a
53 composite endpoint including cryptorchidism, hypospadias, and penile hypoplasia in
54 boys, and a composite outcome including clitoral enlargement, labial fusion, vulvar
55 malformations, and rectovaginal fistula in girls. Secondary outcomes included
56 individual genital malformations and differences in anogenital distance (AGD).

57 GRADE was used to evaluate the level of certainty.

58 **Main results and the role of chance:** Ten observational studies were included.

59 Regarding boys, meta-analysis of the predefined primary outcome could not be
60 performed as no studies reported penile hypoplasia. Another composite endpoint
61 including cryptorchidism and/or hypospadias was reconstructed and no significant
62 association was found with acetaminophen, pooled crude odds ratio (OR) 1.27
63 [95%CI (0.18, 8.94), studies=2, participants=155362, I²=79%, pnet=0.03, REM]. No

64 significant association was found for cryptorchidism or hypospadias separately
65 based on adjusted estimates with pooled OR of 1.02 [95% CI(0.78,1.35), studies=3,
66 participants=155852, I²=32%, pnet=0.23, REM] and 1.02[95%CI(0.89, 1.17),
67 studies=3,participants=159572, I²=40%, pnet=0.19, REM], respectively. No significant
68 difference was found for short AGD. No meta-analysis was possible for girls for any
69 of the predefined outcomes due to lack of data. The level of certainty was low to very
70 low.

71 **Limitations, reasons for caution:** The predefined primary outcomes in boys and girls
72 could not be fully evaluated. Small study effects could not be assessed as the number
73 of included studies was limited. There was significant heterogeneity in the reporting of
74 results and information regarding maternal characteristics was lacking. Lastly, all
75 included studies had a serious or critical risk of bias due to the limited control of
76 confounding factors and the level of certainty was low to very low.
77

78 **Wider implications of the findings:** Acetaminophen remains an indispensable

79 medication and abstaining from pain and fever treatment during pregnancy may

80 have harmful effects on the developing fetus. Further research on external genital

81 malformation risks following *in utero* exposure to acetaminophen should be directed

82 toward developing validated and robust drug-exposure and outcome assessment

83 tools, that control for confounding factors and confounding by indication.

84 **Study funding/competing interest(s):** No funding was used to conduct this study.

85 No relationship or activity could appear to have influenced the submitted work.

86 **Registration number:** CRD42024536483, available from:

87 https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42024536483

88 **Keywords:** neonatal; acetaminophen; urogenital malformations; hypospadias;

89 cryptorchidism

90
91 Introduction

92 Acetaminophen (paracetamol) is a mild analgesic and is currently one of the most
93 commonly used over-the-counter drugs worldwide (Kristensen et al., 2016). Globally,
94 the use of acetaminophen is becoming increasingly prevalent, estimated to be around
95 50% among pregnant women (Bauer et al., 2021; Zafeiri et al., 2021).

96 The US Food and Drug Administration (FDA) and European Medicines Agencies
97 (EMA) have long considered acetaminophen to be of minimal risk when used during
98 pregnancy. However, concerns have been raised as research has shown
99 transplacental passage of acetaminophen and its metabolites, which are speculated
100 to exhibit pharmaceutical effects in the fetus and might disrupt fetal development.
101 Epidemiological studies examining the association between prenatal exposure to
102 acetaminophen and the risk of neurodevelopmental disorders (e.g. attention deficit
103 hyperactivity disorder (ADHD), autism spectrum disorders (ASD) and intellectual
104 disabilities) showed controversial and contradictory results (Brandlistuen et al., 2013;
105 Liew et al., 2014; Ystrom et al., 2017; Damkier et al., 2022). Also, prenatal exposure
106 to acetaminophen has been suggested to be associated with an increased risk of
107 wheezing and asthma in childhood but with inconclusive results (Farquhar et al., 2010;
108 Eyers et al., 2011; Cheelo et al., 2015).

109 Multiple observational studies have also investigated the association between
110 acetaminophen and the occurrence of urogenital malformations and reproductive
111 disorders showing conflicting results. Among urogenital anomalies in males,
undescended testicles (cryptorchidism), the most common urogenital anomaly, is associated with testicular cancer and infertility ("Cryptorchidism," 1992; Boisen et al., 2004; Wood and Elder, 2009). Nevertheless the increased risk of cancer and infertility observed in men with cryptorchidism may reflect underlying primary testicular condition rather than the effect of testicular position itself. Findings from several cohorts suggest an association between prenatal exposure to acetaminophen and increased risk of cryptorchidism (Jensen et al., 2010; Snijder et al., 2012).

Hypospadias defined as the abnormal ventral placement of the urethral opening, is another common urogenital anomaly in males, and data suggest an association with *in utero* exposure to acetaminophen (Baskin et al., 2001; Baskin and Ebbers, 2006; Zafeiri et al., 2022). The anogenital distance (AGD) is also a marker of abnormal androgen activity in males and females, with a shorter distance being an indicator of reproductive toxicity. A large cohort of mother-son pairs reported a shorter anogenital distance in offsprings exposed to acetaminophen or other analgesics *in utero* (Lind et al., 2016). To corroborate these findings, preclinical studies described an association between *in utero* exposure to acetaminophen and increased incidence of cryptorchidism, decreased anogenital distance and testosterone in males rodents, and increased infertility in female rodents (Gupta and Goldman, 1986; Kristensen et al., 2011b; Philibert et al., 2013; Holm et al., 2015). *In vitro* studies focusing on estrogen and testosterone levels in human cells exposed to acetaminophen, showed divergent results (Mazaud-Guittot et al., 2013; van den Driesche et al., 2015; Addo et al., 2021).

Multiple mechanisms are hypothesized to be implicated, including an inhibition of androgen production, an alteration of steroidogenesis, and the disruption of the masculinization process during male fetal development (Gupta and Goldman, 1986; Holm et al., 2015; Addo et al., 2021).
Despite emerging concerns about an association between the use of acetaminophen during pregnancy and developmental outcomes of the endocrine, reproductive, and urogenital systems in both sexes, only one meta-analysis has been published. In 2017 Gurney et al, showed a weak association between prenatal use of analgesics and cryptorchidism (crude pooled odds ratio (OR) of 1.11 [95% confidence interval (CI) (1.00-1.23)]) (Gurney et al., 2017). This study merged all analgesic medications and failed to establish a relation between specific types of analgesics and the risk of occurrence of cryptorchidism.

Given the widespread use of acetaminophen and the rise in urogenital and reproductive disorders, a consensus statement was recently published calling for precautionary action regarding the use of acetaminophen (Bauer et al., 2021), though this paper has been challenged by several groups (Damkier et al., 2022).

## Objectives

In this study, we aimed to investigate the association between acetaminophen exposure during pregnancy and the occurrence of external genital tract malformations in the offspring in both sexes through a systematic review and meta-analysis.
154 Methods

155 This study followed the recommendations of the Cochrane handbook (Higgins Jpt et
156 al., 2024). The protocol was registered in the PROSPERO database
157 (CRD42024536483). This systematic review also followed the Preferred Reporting
158 Items for Systematic reviews and Meta-Analyses (PRISMA) (Moher et al., 2009) and
159 Meta-Analyses of Observational Studies in Epidemiology (MOOSE) (Stroup et al.,
160 2000) reporting guidelines.

161 *Information sources and search strategy:*

162 The search strategy was defined by a team of neonatologists, epidemiologists, and
163 experts in teratogenicity and fetotoxicity. On April 18, 2024, we searched the following
164 electronic databases: MEDLINE via PubMed, EMBASE, Cochrane Database of
165 Systematic Reviews, Cochrane Central Register of Controlled Trials (CENTRAL), the
166 International Clinical Trials Registry Platform (ICTRP), ClinicalTrials.gov along with
167 specialized databases including Reprotox, Shepard's, and TERIS within Micromedex
168 (“Acetamenophen. [database on the Internet]. Greenwood Village (CO): IBM
169 Corporation; 2017,” n.d.). This search was updated on September 20, 2025. A
170 dedicated search algorithm was developed with a set of keywords and free-text words
171 for each database (Supplementary Data File S1).

172 Additionally, a search for abstracts presented in 11 major international meetings from
173 obstetric, pediatric, pediatric endocrinology, teratology, pharmaco-epidemiology and
174 neonatology international societies over the past 5 years was conducted
175 (Supplementary Data File S2).

176 Finally, reference lists from all systematic reviews and selected studies were screened.

177 Following the completion of the initial screening, two Teratology Information Service
178 (TIS) experts (JR and PD) were asked to assess the list of included articles for
179 completeness and to add any additional articles if needed.

180 *Eligibility criteria:*

181 *Study design*

182 Reports of randomized controlled trials (RCTs) and observational studies focusing on
183 the association between *in utero* exposure to acetaminophen and outcomes listed
184 below were included with no restriction on publication dates and languages. Reviews
185 were not included but their references were examined. Expert opinions, editorials,
186 letters, case series and preclinical research studies were not included.

187 *Population, control group and exposure*

188 The study focused on embryos, fetuses, newborns, or children exposed to
189 acetaminophen *in-utero*, regardless of the reason, timing, or duration of exposure, and
190 included control groups of those not exposed to acetaminophen, even if exposed to
191 other medications.

192 *Outcomes*

193 There were two predefined primary composite outcomes: in boys, cryptorchidism,
194 hypospadias, and penile hypoplasia; and in girls, clitoral enlargement, labial fusion,
195 vulvar malformations, and rectovaginal fistula. These outcomes were selected for their
196 prevalence and clinical relevance in the neonatal period, based on the EUROCAT
197 classification (eurocat syndrome guide definition and coding of syndromes., n.d.). In
198 boys, the most frequent genital malformations identifiable at birth are hypospadias and
199 cryptorchidism, both considered part of testicular dysgenesis syndrome, which
200 originates in fetal life. Penile hypoplasia is often associated with these conditions,
201 which supported grouping them into a single composite outcome (Sharpe and
202 Skakkebaek, 2008; Sekaran et al., 2013). In girls, genital examination includes
203 inspection of the labia, clitoris, vulva, and vagina; therefore, clitoral enlargement, labial
204 fusion, vulvar malformations, and rectovaginal fistula were grouped into a composite
205 outcome to capture the full spectrum of anomalies detectable at birth.

206 Secondary outcomes were as follows: the occurrence of cryptorchidism, hypospadias,
207 and penile hypoplasia separately in male offspring, and the occurrence of enlargement
208 of the clitoris, fusion of the labia, congenital rectovaginal fistula, and congenital
209 malformations of the vulva separately in female offspring. We considered mean short
210 and long AGD in boys and girls separately. The short AGD (AGDs) is defined as the
211 distance from the center of the anus to the base of the scrotum in boys, or to the
212 posterior fourchette in girls, and the long ADG (AGDI) is defined as the distance from
213 the center of the anus to the base of the penis in boys or to the clitoris in girls (Salazar-
214 Martinez et al., 2004; Thankamony et al., 2009).

215 Study selection

216 Retrieved records were managed using Zotero v6.030 ("Zotero | About," n.d.), and
217 duplicates were removed. One author (LE) first identified eligible studies by screening
218 titles and abstracts. Then, the full texts of eligible studies were independently reviewed
219 by LE and a second author (KJD) to check for eligibility. All disagreements were
220 resolved through discussion, with the assistance of two other reviewers, an
221 epidemiology expert (BM) and a neonatology expert (DM), to reach a consensus.
222 Reasons for exclusion were reported in a flowchart summarizing the selection process.
223 When the full text was missing, the authors of the study were contacted to obtain the
224 detailed results or the full text. If the authors did not reply, the study was excluded from
225 the systematic review. Full texts that were not in English were translated using Google
226 Translate to check for eligibility.

227 Data extraction

228 Two authors (LE and KJD) independently extracted data from the included studies
229 using a standardized data extraction grid. All disagreements were resolved through
230 discussion, with the assistance of two reviewers (BM and DM) to reach a consensus.
231 In cases of missing or unclear data in the manuscript, an attempt was made to contact
232 the study authors. Full texts that were not in English were translated using Google
233 Translate to extract data.

234 *Data Collection*

235 For each of the included studies, general characteristics of the study, as well as
236 information pertaining to the study populations, drug exposure, and maternal and
237 offspring outcomes were collected by LE and KJD. Collected study results included
238 measures of association (odds ratios (OR), relative risk (RR) and hazards ratios (HR)),
239 and mean differences (MD), along with standard deviation for continuous variables.
240 Regarding the primary outcome measure, the composite criterion was planned to be
241 either collected from original papers or reconstructed after data extraction and
242 collection, following, if needed, contact with the authors. (Further details about data
243 collection are provided in Supplementary Data File S1).

244 *Risk of bias assessment*

245 The risk of bias (ROB) was independently assessed by two review authors (LE and
246 KJD) with the updated versions of ROBINS-I (Sterne et al., 2016) for non-randomized
247 studies. The assessment of bias was performed focusing on the primary outcomes. In
248 cases where the primary outcomes were not reported in the paper, ROB was
249 evaluated for the reported outcome(s). All disagreements were resolved by discussion
250 with the help of two other reviewers (BM and DM) to reach consensus.
251 *Data synthesis*

252 *Measures of association*

253 For binary outcomes, ORs were used as the measure of association. If the measures
254 of association provided in the article were RR or HR, they were considered equivalent
255 to ORs, as all the outcomes considered here are rare (VanderWeele, 2020). For
256 continuous outcomes (anogenital distance), MD was used.

257 *Meta-analysis*

258 For the primary outcomes, the planned main analysis was a meta-analysis of the
259 association between acetaminophen exposure and external genital tract
260 malformations (composite endpoint) in boys and girls separately. We planned to
261 reconstruct the composite outcome by pooling the number of events from studies
262 reporting all the outcomes of interest. Separate meta-analyses were planned for each
263 secondary outcome: hypospadias, cryptorchidism, and short and long anogenital
264 distance in boys and girls separately.

265 As recommended by the Cochrane Collaboration, both fixed-effect (FEM) and random-
266 effects (REM) models were performed and the results compared. Since the REM may
267 be influenced by small-study effects, both models were examined to ensure the
268 robustness of the findings. Nevertheless, in the manuscript, we preferentially report
269 the results from the REM, as this model is more appropriate when clinical and
270 methodological heterogeneity is expected, which is the case here.

271 For binary outcomes, the Mantel-Haenszel method without continuity correction was
272 used for the fixed-effect model (FEM) and the Der Simonian-Laird method was used
273 for the random-effects model (REM) (Higgins Jpt et al., 2024; DerSimonian and Laird,
274 1986). The meta-analysis was based on adjusted ORs if possible, and on crude ORs
275 when adjusted ORs were not reported, or where risk estimates were reconstructed
276 from crude outcome data. For continuous outcomes, the inverse-variance weighting
277 method was used for FEM and the restricted maximum likelihood estimator for REM.

278 Statistical heterogeneity between studies was evaluated by visually examining forest
279 plots and by using Cochran's Q-test and I². An I² value greater than 50% or a p-value
280 less than 0.1 was used to indicate substantial heterogeneity (Rücker G et al., 2008;
281 Lin, 2020).

282 *Sensitivity and subgroup analysis*

283 A sensitivity analysis was performed to assess the robustness of the results using only
284 adjusted ORs. Sensitivity analyses were also performed based on the timing of
285 exposure, i.e. during the first versus second or third trimesters of pregnancy. Subgroup
286 analyses were performed according to the ROB, i.e. taking into consideration studies
287 with a critical ROB versus those in other ROB categories.
288 Assessment of small study effect

289 Small study effect could not be assessed for all the outcomes, given the small (<10)

290 number of studies included for each outcome.

291 All analyses were performed using R software version 4.2.2 (R Core Team (2021).,

292 n.d.), using the following packages: meta (v 7.0-0), metafor (v 4.6-0), dplyr (v 1.1.4),

293 robvis (v 0.3.0), tidyverse (v2.0.0), grid, and readxls (v1.4.3)(Wickham H et al., 2024;

294 Viechtbauer, 2010; Balduzzi et al., 2019; McGuinness and Higgins, 2021; "Companion

295 R Package for the Guide Doing Meta-Analysis in R," n.d.; "Journal of Open Source

296 Software: Welcome to the Tidyverse," n.d.).

297 Certainty of evidence

298 The certainty of evidence for all the outcomes was assessed using the Grading of

299 Recommendations, Assessment, Development and Evaluations (GRADE) approach

300 (Guyatt et al., 2008) and GRADEpro software (McMaster University and Evidence

301 Prime., n.d.).
302 **Results**

303 **Literature search and study selection**

304 The initial searches yielded a total of 13,401 records. After removing duplicates, 305 12,444 records were screened on title and abstract. A total of 12,389 records were 306 excluded, with reasons for exclusion detailed in the PRISMA flowchart (Fig. 1). Among 307 the remaining 55 articles assessed for eligibility, 12 studies fulfilled the eligibility 308 criteria. Ten studies, encompassing a total of 273,915 offspring, were included in the 309 final analysis (Rebordosa et al., 2008; Jensen et al., 2010; Kristensen et al., 2011a; 310 Poletta et al., 2012; Snijder et al., 2012; Fisher et al., 2016; Lind et al., 2016; Interrante 311 et al., 2017; Navarro-Lafuente et al., 2021; Zafeiri et al., 2022), the remaining two 312 studies (Feldkamp et al., 2010; Lind et al., 2013), were excluded as they originated 313 from the same registry as the study by Interrante et al., therefore only the latter was 314 included (Interrante et al., 2017). Two TIS experts (PD and JR) examined the list of 315 included records and suggested three studies previously excluded at the screening 316 phase since they did not meet eligibility criteria (two did not report malformations after 317 *in-utero* exposure to acetaminophen (Aselton et al., 1985; Correy et al., 1991), the third 318 was a basic science study (Gonzalez et al., 2020)).

319 **Study and population characteristics**

320 Table 1 summarizes the characteristics of the ten included articles. There were eight 321 cohorts (Rebordosa et al., 2008; Jensen et al., 2010; Kristensen et al., 2011a; Snijder
322 et al., 2012; Fisher et al., 2016; Lind et al., 2016; Navarro-Lafuente et al., 2021; Zafeiri
323 et al., 2022) and two case control studies (Poletta et al., 2012; Interrante et al., 2017).

324 There was no RCT. The majority of the studies had a retrospective design (n=6)
325 (Rebordosa et al., 2008; Jensen et al., 2010; Poletta et al., 2012; Snijder et al., 2012;
326 Interrante et al., 2017; Zafeiri et al., 2022). Most of the included studies were
327 performed in a population-based setting and originated from European countries
328 (Denmark (n=4), UK (n=2), Spain (n=1) and the Netherlands (n=1)) (Rebordosa et al.,
329 2008; Jensen et al., 2010; Kristensen et al., 2011a; Snijder et al., 2012; Fisher et al.,
330 2016; Lind et al., 2016; Navarro-Lafuente et al., 2021; Zafeiri et al., 2022). The
331 remaining two studies were conducted in the USA, and Brazil/Argentina (Poletta et al.,
332 2012; Interrante et al., 2017). The inclusion period ranged from 1967 to 2018.
333 Population characteristics are summarized in Supplementary Table S1.

334 Definition and period of exposure

335 Acetaminophen exposure was measured via self-reported questionnaires, telephone,
336 or computer-assisted interviews in most studies, where pregnant women reported the
337 use of acetaminophen either alone (Kristensen et al., 2011a; Snijder et al., 2012; Lind
338 et al., 2016; Interrante et al., 2017; Navarro-Lafuente et al., 2021; Zafeiri et al., 2022),
339 with other painkillers (Rebordosa et al., 2008; Jensen et al., 2010; Fisher et al., 2016),
340 or as part of unspecified medications (Poletta et al., 2012). Exposure periods varied
341 across studies, with varying trimester definitions. Most studies reported
342 acetaminophen use across all three trimesters (Jensen et al., 2010; Kristensen et al.,
343 2011a; Fisher et al., 2016; Lind et al., 2016; Navarro-Lafuente et al., 2021), while
344 others focused solely on the first trimester (Rebordosa et al., 2008; Poletta et al., 345 2012), or on exposure anytime during pregnancy (Interrante et al., 2017; Zafeiri et al., 346 2022). The duration of exposure was reported in three studies, ranging from one day 347 to more than four weeks (Jensen et al., 2010; Kristensen et al., 2011a; Navarro- 348 Lafuente et al., 2021).

349 **Comparator**

350 In all studies, the comparator group consisted of participants with no medication
351 exposure, except for one study where comparator subjects were exposed to other
352 painkillers, including non-steroidal anti-inflammatory drugs (NSAID) and aspirin
353 (Snijder et al., 2012).

354 **Outcomes**

355 In boys, the predefined composite primary outcome of hypospadias, cryptorchidism,
356 or penile hypoplasia was not evaluated in any of the included studies. Specifically,
357 cryptorchidism was assessed in six studies (Rebordosa et al., 2008; Jensen et al.,
358 2010; Kristensen et al., 2011a; Snijder et al., 2012; Fisher et al., 2016; Zafeiri et al.,
359 2022), and hypospadias in five (Rebordosa et al., 2008; Poletta et al., 2012; Snijder et
360 al., 2012; Interrante et al., 2017; Zafeiri et al., 2022). Some studies reported both
361 cryptorchidism and hypospadias (Rebordosa et al., 2008; Snijder et al., 2012; Zafeiri
362 et al., 2022). There was no consistent reporting on whether these malformations were
363 isolated or co-occurred with other defects. Only one study assessed penile length
364 without providing a cutoff for hypoplasia, (Fisher *et al.*, 2016) and another reported 365 penile width without categorization (Lind *et al.*, 2016). For this reason, penile 366 hypoplasia could not be assessed. The corresponding authors of all the included 367 articles were contacted for clarification, however no additional data was obtained as 368 they either no longer had access to the data or did not respond. Cryptorchidism and 369 hypospadias were defined either using ICD-10 codes (Rebordosa *et al.*, 2008; Jensen 370 *et al.*, 2010; Zafeiri *et al.*, 2022) or a clinical definition that was consistent across 371 studies (Kristensen *et al.*, 2011a; Snijder *et al.*, 2012; Fisher *et al.*, 2016). AGD in boys 372 was reported in three studies; two studies included both short and long AGD (Lind *et 373 al.*, 2016; Navarro-Lafuente *et al.*, 2021), and one study reported only short AGD 374 (Fisher *et al.*, 2016). The age of AGD measurement ranged from birth to 24 months. 375 In girls, no studies reported the predefined composite primary outcome (clitoral 376 enlargement, labial fusion, vulvar malformations, or rectovaginal fistula), nor were 377 these outcomes reported individually. The only outcomes reported in girls were short 378 and long AGD. (Fisher *et al.*, 2016; Lind *et al.*, 2016).

379 **Risk of bias assessment**

380 Six studies were judged to have a serious ROB, and four were judged to have a critical 381 ROB. These results were mainly driven by bias due to confounding, where 382 confounding was either uncontrollable (n=6) or only a small number of relevant 383 confounding factors were considered (n=4) (Fig. 2).

384 **Meta-analyses**
Meta-analyses could be only performed for boys since there was no reported data in the literature concerning the primary or secondary outcomes in girls, except for AGD where separate meta-analyses were performed for boys and girls.

### Primary outcome

In boys, since the originally predefined composite outcome could not be evaluated, another composite outcome evaluating hypospadias or cryptorchidism was reconstructed using data from two studies considering acetaminophen exposure at any time during pregnancy (Rebordosa et al., 2008; Zafeiri et al., 2022). The study by Snijder et al (Snijder et al., 2012) was not included in this analysis since they only reported outcomes according to the trimester of exposure without reporting results for the overall population. The total number of subjects in the pooled analysis was 155,362 with 38,778 offspring in the exposed group and 116,584 in the unexposed group. Although the precision of our estimate was low, and the estimate was based on pooled unadjusted point estimates, we found no association between *in-utero* exposure to acetaminophen at any time during pregnancy and the occurrence of the composite outcome of hypospadias and/or cryptorchidism; pooled crude OR of 1.27 [95%CI (0.18,8.94),I²= 79%, phet=0.03, REM] (Fig.3a).

### Secondary outcomes

Concerning cryptorchidism, a meta-analysis using adjusted OR was performed on three studies (Rebordosa et al., 2008; Kristensen et al., 2011a; Zafeiri et al., 2022)
405 with a total of 155,852 children. Although a statistically significant association was 406 found when crude ORs were pooled (OR 1.33 [95%CI; 1.08 to 1.64], I²=0, p_het=0.93, 407 REM) (Supplementary Fig. S1), there was no significant association between in-utero 408 exposure to acetaminophen at any time during pregnancy and the occurrence of 409 cryptorchidism when adjusted ORs were pooled (aOR 1.02 [95%CI; 0.78 to 1.35], 410 I²=32%, p_het=0.23, REM). (Fig. 3b). Sensitivity analyses using adjusted OR, showed no 411 significant association after excluding studies with combined painkiller use 412 (Rebordosa et al., 2008) or with a critical ROB (Kristensen et al., 2011a) 413 (Supplementary Figs. S2-S3).

414 Regarding hypospadias, no significant association was found with in-utero exposure 415 to acetaminophen during pregnancy, for either the crude analyses with a pooled crude 416 OR 1.03[95% CI (0.88,1.20), I² =0, p=0.68, REM] (Supplementary Fig. S4), nor in the 417 adjusted analyses with a pooled adjusted OR 1.02 [95% CI (0.89,1.17), I²= 40%, p_het= 418 0.19, REM] (Fig. 3c). Results were consistent in the sensitivity analyses performed 419 using adjusted OR, when excluding studies with combined painkiller use or reporting 420 hypospadias in live births (Rebordosa et al., 2008; Zafeiri et al., 2022) (Supplementary 421 Figs. S5-S6).

422 Regarding AGD at birth in boys, meta-analysis was possible only for AGDs. The 423 analysis was conducted on two studies (Fisher et al., 2016; Navarro-Lafuente et al., 424 2021) involving 958 children. No significant difference was found between groups for 425 AGDs, with a pooled MD of 0.00 [95% CI (-0.07, 0.08), I²=0%, p_het=0.90, REM] (Fig. 426 4a). Similarly, no significant difference was found when using the adjusted MD with a
pooled MD of -0.02 [95% CI (-0.14, 0.10), I²= 0%, phet=0.86, REM] (Fig. 4b). The study by Lind et al. was excluded from this analysis since the authors did not provide the SD.

Fixed effects model meta-analyses did not yield different results compared to REM, except for analyses of the crude results for hypospadias and for the reconstructed composite outcome (Fig. 3a and Supplementary Fig. S4). which displayed statistically significant associations.

In girls, there was no published data on the secondary outcomes except for short and long AGD. However, the meta-analysis could not be performed due to lack of data.

The single study found no difference in mean AGDs (MD of -0.01 [95% CI (-0.07, 0.05)]). (Fisher et al., 2016)

Sensitivity analyses- stage of pregnancy exposure

We performed a sensitivity analysis according to the timing of exposure during
pregnancy. The reconstructed composite outcome could not be assessed according
to trimester of exposure as these results were not reported in the studies used for this
outcome (Rebordosa et al., 2008; Zafeiri et al., 2022). As regards cryptorchidism, there
was no significant association between in utero exposure to acetaminophen in the first
trimester (T1) and cryptorchidism with a pooled adjusted OR of 0.99 [95% CI (0.79,
1.22), I² = 0%, phet=0.45, REM] (Supplementary Fig. S7) and a pooled crude OR of
1.44 [95% CI (0.76, 2.75), I² = 0%, phet=0.83, REM] (Supplementary Fig. S8). Similar
447 results were obtained for the second trimester (T2) with a pooled adjusted OR of 1.33
448 [95% CI (0.87, 2.04), I² = 35%, phet= 0.21, REM] (Supplementary Fig. S9). No
449 sensitivity analysis could be performed for hypospadias by timing of exposure.

450 Regarding AGD in boys, sensitivity analysis was only possible for AGDs with no
differences found in either T1 or T2 (Fig 4c-4d).

452 Subgroup analyses- risk of bias

453 We performed a subgroup analysis according to ROB for each of the separate
454 secondary outcomes (cryptorchidism and hypospadias). This analysis was not
455 possible for the composite outcome as both included studies had a similar serious
456 ROB. For cryptorchidism, in utero exposure to acetaminophen showed no differential
457 effect based on interaction test for subgroup differences depending on ROB (serious
458 vs critical) (p=0,41, REM). (Supplementary Fig. S10) In contrast, for hypospadias, the
459 differential effect of acetaminophen according to ROB was statistically significant with
460 a p value of <0.01 (Supplementary Fig. S11). This indicates that the observed
461 association between exposure to acetaminophen and hypospadias was most likely
462 driven by studies with a high ROB.

463 GRADE summary of findings

464 The GRADE summary of findings for all outcomes is presented in Table 2. For most
outcomes, the certainty of the evidence was rated as very low due to multiple
466 downgrading factors. First, the risk of bias was high, as all included studies were
467 observational, raising concerns about confounding and measurement bias (six studies
468 were judged to have a serious risk of bias, and four a critical risk). In addition,
469 inconsistency (heterogeneity) contributed to downgrading the certainty of the
470 composite outcome for boys. Imprecision also led to downgrading, as many effect
471 estimates had wide confidence intervals (e.g., for the composite outcome of
472 hypospadias and/or cryptorchidism: OR 1.27, 95% CI 0.18–8.94), and some
473 outcomes, such as AGD, were based on a small number of participants. Only the
474 outcome of hypospadias was rated as low certainty, as its results were more precise.

475

476
477 Discussion

478 *Summary of the results*

479 In this systematic review and meta-analysis, we identified 10 observational studies examining the association between *in-utero* exposure to acetaminophen and the occurrence of genital malformations and modified AGD in boys. No significant association was found between *in-utero* exposure to acetaminophen and the occurrence of the combined endpoint of cryptorchidism or hypospadias, cryptorchidism, hypospadias or modified AGDs, though precision of pooled estimates were sometimes low. Additionally, sensitivity analyses examining timing of exposure (restricting to T1 or T2) did not identify associations with cryptorchidism or differences in AGD. The level of evidence was rated as very low for most outcomes. In girls, no studies reported data on external genital tract malformations. Therefore, no systematic review or meta-analysis was possible for any of the outcomes in girls

490

491 *Interpretation of principal findings*

492 Our findings provide little evidence to support the hypothesis of a clinically meaningful association between *in utero* exposure to acetaminophen and external genital tract malformations. However, these results should be interpreted with caution due to the multiple limitations of the included studies and the low level of evidence.
In particular, for the reconstructed composite outcome, we combined data from two studies (Rebordosa et al., 2008; Zafeiri et al., 2022) describing hypospadias and cryptorchidism. Our results likely overestimate the association since detailed information on whether these malformations were isolated or combined was lacking, and our composite outcome resulted from the sum of the number of events for each outcome. Both hypospadias and cryptorchidism can indicate testicular dysgenesis, with cryptorchidism co-occurring in about 10% of hypospadias cases (Tasian et al., 2010; Sekaran et al., 2013).

For the composite outcome as well as for hypospadias specifically, we observed a variation in the results between the FEM and REM, which may be due to heterogeneity. While it can be biased in case of small study effect, REM is more appropriate when clinical and methodological heterogeneity is expected, which is the case here. Small study effect could not be ruled out as publication bias could not be assessed for all outcomes, and selective outcome reporting could not be excluded (Fig.2). One of the causes of this heterogeneity was major inter-study differences in acetaminophen exposure. In detail, one study (Zafeiri et al., 2022) reported acetaminophen as the sole exposure, while in the other (Rebordosa et al., 2008), it was combined with other prescribed or over-the-counter medications. Furthermore, differences in data collection methods and timing of exposure contribute to the observed heterogeneity. Comparing maternal characteristics between studies was not possible since Rebordosa et al. did not report them (Rebordosa et al., 2008).
The only consistent pattern of association was observed for cryptorchidism, however this was based solely on crude estimates, making data confounding highly likely. Our meta-analysis was limited by the small number of included studies (Kristensen et al., 2011a; Zafeiri et al., 2022) and the absence of reported crude ORs in other studies (Rebordosa et al., 2008; Jensen et al., 2010; Snijder et al., 2012; Fisher et al., 2016).

In Kristensen et al., cryptorchidism was diagnosed at birth without further follow-up details to confirm the diagnosis. Since an estimated half of cryptorchidism cases have delayed testicular descent until 10-12 weeks after birth (Tasian et al., 2010; Leslie et al., 2024), this study may have overestimated the clinical relevance of cryptorchidism.

Similarly, Zafeiri et al. did not provide information on the age at diagnosis or follow-up. After adjusting for only a few confounding factors, the apparent association for cryptorchidism became non-significant, highlighting the impact of confounding in this context. In the same manner, the significance in the association observed for hypospadias in the FEM was primarily driven by a single study (Poletta et al., 2012).

In this case the high heterogeneity between studies makes the meta-analysis uninterpretable for the FEM, especially since the study responsible for this high heterogeneity has a critical ROB due to poor handling of confounding bias.

Despite the authors' attempt to adjust for confounding factors, most studies lacked control for key variables, leading to serious or critical risk of bias. Factors like placental insufficiency, hypertensive disorders, and small for gestational age were often unaccounted for, despite evidence linking them to increased risk of genital malformations (Shan et al., 2023). Indeed, placental insufficiency can disrupt the androgen axis and placental human chorionic gonadotropin (hCG), both essential for testosterone production, which in turn is crucial for urethral closure and testicular
descent potentially leading to hypospadias and cryptorchidism (Chen et al., 2017; Arendt et al., 2018; Wang et al., 2022). Moreover, prenatal exposure to endocrine-disrupting chemicals can reduce testosterone and insulin-like 3 peptide (INSL3) production, thereby posing a risk for external genital tract malformations (Gaspari et al., 2011). Additionally, family history is a crucial factor to consider, as genetic mutations in INSL3 may contribute to cryptorchidism, while hypospadias has a familial occurrence, affecting about 9% of fathers and 14% of brothers of offsprings with the condition (Brouwers et al., 2007).

An important element affecting these associations is also confounding by indication. Except for three studies, the included studies did not report maternal characteristics or control for the reasons acetaminophen was used (Rebordosa et al., 2008; Jensen et al., 2010; Snijder et al., 2012). The MotherToBaby birth cohort showed that women with conditions such as arthritis, fever, chronic pain, or headaches were more likely to use acetaminophen (Bandoli et al., 2020). Maternal fever or infection during pregnancy can disrupt placental angiogenesis, leading to various congenital anomalies (Dreier et al., 2014; Weckman et al., 2019; An et al., 2022).

Other established prenatal risk factors such as smoking, alcohol, and co-medication use were insufficiently accounted for in the underlying studies. Only one controlled for smoking (Jensen et al., 2010) while none reported concomitant use of alcohol or teratogenic medications.
Another important factor in the occurrence of genital tract malformations is the timing of exposure. Sexual differentiation begins at around 9 weeks of gestation and penile development reaches its final stage by 17 weeks (Baskin et al., 2018; Shen et al., 2018; Cunha et al., 2020). Therefore, the first trimester is crucial when considering hypospadias. For cryptorchidism, testicular descent starts between 25 and 30 weeks of gestation, making the second trimester the key period to consider for this malformation (Hutson et al., 2013). A sensitivity analysis by trimester was only possible for cryptorchidism using three studies (Jensen et al., 2010; Kristensen et al., 2011a; Snijder et al., 2012) revealing no significant associations. consistent with findings of the included cohort.

We also examined the association between acetaminophen and AGD, a widely accepted marker of androgen exposure, primarily used in experimental reproductive toxicology (Thankamony et al., 2009). In rodent models, where perineal growth depends on dihydrotestosterone, shortened AGD is associated with a higher risk of hypospadias and cryptorchidism (Philippa D.Darbre, 2015) In humans, both AGD and penile length have been reported to be reduced in boys with these malformations, supporting the biological plausibility of AGD as an early indicator of disrupted androgen signaling (Darbre, 2015). Unlike Fisher et al. (Fisher et al., 2016), who reported a mean difference in AGDs in boys exposed between 8 and 14 weeks of gestation, suggestive of the male masculinization programming window (Welsh et al., 2008; Sharpe, 2020), our meta-analysis found no significant difference in mean AGDs after *in utero* acetaminophen exposure, even when stratified by trimester. This lack of association could be due to the limited number of available studies (Fisher et al., 2016;
584 Navarro-Lafuente et al., 2021), missing data or inter-study variation in times of
585 measurement. (Lind et al., 2016)

586 Regarding outcomes in girls, we believe the gap in the literature may be due to several
587 factors. We must acknowledge that we decided a priori to study genital outcomes in
588 girls that can be identified at birth but that those outcomes are more likely to be
589 associated with hyperandrogenism, whereas the potential consequences of
590 acetaminophen exposure, according to the underlying hypothesis, may be more
591 closely related to hypoandrogenism due to disrupted testosterone production. Second
592 , genital examination in girls during the neonatal period is more challenging compared
593 with boys; the classification and categorization of female genital anomalies is more
594 complex and less standardized; and these malformations are not systematically
595 recorded in registries.

596 *Comparison with previous meta-analyses*

597 A meta-analysis conducted in 2017 (Gurney et al., 2017) found that any use of
598 analgesics during pregnancy, compared to never-use, was associated with a slightly
599 increased risk of cryptorchidism, with a pooled crude OR of 1.11 [95% CI (1.00–1.23)]
600 that may be affected by confounding factors. This is consistent with one of our findings
601 on the occurrence of cryptorchidism, but, particularly, prior to adjustment. However, it
602 is important to note that this former meta-analysis combined various analgesics
603 (aspirin, acetaminophen, NSAIDs, dipyrone, and unspecified analgesics) without
604 stratifying by type of medication, and did not account for any adjustments for
605 confounding factors.

606 *Strength and limitations*

607 Our study has significant strengths. To our knowledge, this is the first systematic
608 review and meta-analysis investigating the association between *in utero* exposure to
609 acetaminophen and external genital tract malformations. We conducted an extensive
610 search via electronic databases and grey literature and included 273,915 offsprings in
611 our final analysis. We followed the recommendations from the Cochrane handbook
612 regarding study selection, data extraction, ROB assessment and data synthesis. We
613 also investigated the effect of confounding factors as well as the effect of timing and
614 duration of exposure to acetaminophen during pregnancy. Although we could not
615 perform a meta-analysis for female outcomes, our study is the first study aiming to
616 investigate external genital tract malformations in this population, and drawing
617 attention to the lack of reporting of genital tract malformations in girls.

618 Our study also has some important limitations. First, the originally predefined
619 composite primary outcomes in boys and girls could not be fully evaluated, which
620 represents a major limitation. Second, only a limited number of studies were included
621 in the final analysis, thus small study effect could not be assessed. Third, included
622 studies had significant heterogeneity in reporting of results as well as lacked
623 information specifically in terms of maternal characteristics. Fourth, all the included
624 records were observational studies, hence we cannot rule out recall bias or
misclassification of exposure, specifically as the assessment of exposure to acetaminophen was carried out by interviews or auto questionnaires in all included studies. There were no randomized controlled trials, which is not surprising given the ethical issues involved in conducting such studies in pregnant women. Fifth, all the included studies were judged as having serious or critical ROB due to the limited control of confounding factors. Sixth, none of the studies investigated the cumulative dose effect of acetaminophen, preventing us from assessing any potential link with chronic use. In fact, the duration of exposure was reported in only three studies (Jensen et al., 2010; Kristensen et al., 2011a; Navarro-Lafuente et al., 2021) for different outcomes and in a heterogeneous manner. Seventh, most of the included studies were conducted using population-based administrative datasets with restricted access, limiting the authors' ability to share detailed data from their studies. The use of administrative datasets as a method for assessing outcomes can undermine the validity of data since the reported outcomes in these studies are not verified clinically for each individual subject. Finally, a universal and uniform definition of external congenital genital tract malformation is lacking. The existing ICD-10 and EUROCAT classifications (eurocat syndrome guide definition and coding of syndromes., n.d.) list all known genital tract malformations without categorizing them by clinical relevance, hindering their practical application for clinical and research purposes.

644

645 Conclusion
646 This meta-analysis did not find evidence to support a clinically meaningful association
647 between *in utero* acetaminophen exposure and external genital malformations in boys.

648 The underlying studies were of low to very-low methodological quality and future
649 studies should address this issue. Further research on external genital malformation
650 risks following *in utero* exposure to acetaminophen should be directed toward
651 developing validated and robust drug exposure and outcome assessment tools,
652 especially in girls.

653 **Data availability:** All data are incorporated into the article and its supplementary
654 material. Data extracted from original articles as well as R analytic code can be
655 provided by the authors upon request.

656 **Acknowledgment:** We thank DMU ESPRIT for the internship grant and the Centre
657 Hospitalier du Mans for the masters grant.

658 **Authors' roles:** BM, DM, EE and LE conceptualized the study. Methodology was
659 carried out by BM, DM, AD and LE. Literature search was performed by LE. Data
660 curation was done by LE and KJD. PD and JR reviewed the list of included articles to
661 check for its completeness and helped to interpret results. Formal analysis was
662 performed by LE. Original draft was written by LE, edited by DM and BM, and
663 reviewed by all the authors

664 **Funding:** No funding was used to conduct this study.
665 **Conflict of interest:** No relationship or activity could appear to have influenced the

666 submitted work.

667
668 **Figure legends**

669 **Fig. 1: Study flowchart**

670 ICTRP: International clinical trials registry platform

671 **Fig. 2: Traffic lights plot for risk of bias**

672 **Fig. 3: Results of the meta-analysis for the primary and secondary outcomes in**

673 **boys** Forest plots showing the meta-analysis for the occurrence of the composite

674 outcome of cryptorchidism and/or hypospadias (a), hypospadias (b) and

675 cryptorchidism (c) in boys after exposure to acetaminophen at any time during

676 pregnancy. OR: odds ratio

677 **Fig. 4: Meta-analysis for short anogenital distance in boys** Forest plots showing

678 the meta-analysis for anogenital distance in boys following exposure to

679 acetaminophen at any time during pregnancy (a), during the first trimester (b), or

680 during the second trimester (c). MD: mean difference
681 Supplementary figure S1: Meta-analysis for cryptorchidism after exposure to
682 acetaminophen at any time during pregnancy using crude odds ratios

683 OR: odds ratio

684 Supplementary figure S2: Sensitivity analysis for cryptorchidism excluding
685 studies reporting the use of acetaminophen combined with other pain killers

686 OR: odds ratio

687 Supplementary figure S3: Sensitivity analysis for cryptorchidism including
688 studies with a serious risk of bias only

689 OR: odds ratio

690 Supplementary figure S4: Meta-analysis for hypospadias after exposure to
691 acetaminophen at any time during pregnancy using crude odds ratios

692 OR: odds ratio

693 Supplementary figure S5: Sensitivity analysis for hypospadias after exposure
to acetaminophen at any time during pregnancy excluding studies reporting
the use of acetaminophen combined with other pain killers
696 OR: odds ratio

697 Supplementary figure S6: Sensitivity analysis for hypospadias including

698 studies that only have live births after exposure to acetaminophen at any time

699 during pregnancy

700 OR: odds ratio

701 Supplementary figure S7: Meta-analysis for cryptorchidism after exposure in

702 the first trimester using adjusted odds ratios

703 OR: odds ratio

704 Supplementary figure S8: Meta-analysis for cryptorchidism after exposure in

705 the first trimester using crude odds ratios

706 OR: odds ratio

707 Supplementary figure S9: Meta-analysis for cryptorchidism after exposure in

708 the second trimester using adjusted odds ratios

709 OR: odds ratio
710 Fig. S10: Subgroup analysis according to risk of bias for cryptorchidism using

711 adjusted odds ratios

712 OR: odds ratio

713 Supplementary figure S11: Subgroup analysis according to risk of bias for

714 hypospadias using crude odds ratios

715 OR: odds ratio

716

717
718 References

719 Acetamenophen. [database on the Internet]. Greenwood Village (CO): IBM Corporation; 2017Available from:
https://www.micromedexsolutions.com/.

721 Addo KA, Palakodety N, Fry RC. Acetaminophen Modulates the Expression of Steroidogenesis-Associated
722 Genes and Estradiol Levels in Human Placental JEG-3 Cells. *Toxicol Sci* [Internet] 2021;179:44–52.

723 An H, Zheng W, Zhu Q, Wen H. Retrospective study of intrapartum fever in term pregnancies and adverse
724 obstetric and neonatal outcomes. *PeerJ* [Internet] 2022;10:e14242.

725 Arendt LH, Henriksen TB, Lindhard MS, Parner ET, Olsen J, Ramlau-Hansen CH. Hypertensive Disorders of
726 Pregnancy and Genital Anomalies in Boys: A Danish Nationwide Cohort Study. *Epidemiol Camb Mass*
727 2018;29:739–748.

728 Aselton P, Jick H, Milunsky A. First-trimester drug use and congenital disorders. *Obstet Gynecol* [Internet]
729 1985;65:451–455.

730 Balduzzi S, Rücker G, Schwarzer G. How to perform a meta-analysis with R: a practical tutorial. *Evid Based Ment*
731 *Health* 2019;22:153–160.

732 Bandoli G, Palmsten K, Chambers C. Acetaminophen use in pregnancy: Examining prevalence, timing, and
733 indication of use in a prospective birth cohort. *Paediatr Perinat Epidemiol* 2020;34:237–246.

734 Baskin L, Shen J, Sinclair A, Cao M, Liu X, Liu G, Isaacson D, Overland M, Li Y, Cunha GR. Development of the
735 human penis and clitoris. *Differ Res Biol Divers* 2018;103:74–85.

736 Baskin LS, Ebbers MB. Hypospadias: anatomy, etiology, and technique. *J Pediatr Surg* 2006;41:463–472.

737 Baskin LS, Himes K, Colborn T. Hypospadias and endocrine disruption: is there a connection? *Environ Health*
738 *Perspect* 2001;109:1175–1183.
739 Bauer AZ, Swan SH, Kriebel D, Liew Z, Taylor HS, Bornehag C-G, Andrade AM, Olsen J, Jensen RH, Mitchell RT, et al. Paracetamol use during pregnancy — a call for precautionary action. *Nat Rev Endocrinol* [Internet] 2021;17:757–766.

742 Boisen K, Kaleva M, Main K, Virtanen H, Haavisto A-M, Schmidt I, Chellakooty M, Damgaard I, Mau C, Reunanen M, et al. Difference in prevalence of congenital cryptorchidism in infants between two Nordic countries. *The Lancet* [Internet] 2004;363:1264–1269.

745 Brandlistuen RE, Ystrom E, Nulman I, Koren G, Nordeng H. Prenatal paracetamol exposure and child neurodevelopment: a sibling-controlled cohort study. *Int J Epidemiol* 2013;42:1702–1713.

747 Brouwers MM, Feitz WFJ, Roelofs LAJ, Kiemeney LALM, De Gier RPE, Roeleveld N. Risk factors for hypospadias. *Eur J Pediatr* [Internet] 2007;166:671–678.

749 Cheelo M, Lodge CJ, Dharmage SC, Simpson JA, Matheson M, Heinrich J, Lowe AJ. Paracetamol exposure in pregnancy and early childhood and development of childhood asthma: a systematic review and meta-analysis. *Arch Dis Child* 2015;100:81–89. England.

752 Chen Y, Sun L, Geng H, Lei X, Zhang J. Placental pathology and hypospadias. *Pediatr Res* [Internet] 2017;81:489–495.

754 Companion R Package for the Guide Doing Meta-Analysis in RAvailable from: https://dmetar.protectlab.org/.

755 Correy JF, Newman NM, Collins JA, Burrows EA, Burrows RF, Curran JT. Use of prescription drugs in the first trimester and congenital malformations. *Aust N Z J Obstet Gynaecol* 1991;31:340–344.

757 Cryptorchidism: a prospective study of 7500 consecutive male births, 1984-8. John Radcliffe Hospital Cryptorchidism Study Group *Arch Dis Child* 1992;67:892–899.

759 Cunha GR, Sinclair A, Cao M, Baskin LS. Development of the human prepuce and its innervation. *Differ Res Biol* *Divers* 2020;111:22–40.
761 Damkier P, Cleary B, Weber-Schoendorfer C, Shechtman S, Cassina M, Panchaud A, Diav-Cirtin O. Handle with care - interpretation, synthesis and dissemination of data on paracetamol in pregnancy. *Nat Rev Endocrinol* 2022;18:191.

764 Darbre PD. Chapter 9 - Endocrine Disruption and Male Reproductive Health. In Darbre PD, editor. *Endocr Disrupt Hum Health* [Internet] 2015; p. 159-175. Academic Press: BostonAvailable from: https://www.sciencedirect.com/science/article/pii/B9780128011393000090.

767 DerSimonian R, Laird N. Meta-analysis in clinical trials. *Control Clin Trials* 1986;7:177-188.

768 Dreier JW, Andersen A-MN, Berg-Beckhoff G. Systematic Review and Meta-analyses: Fever in Pregnancy and Health Impacts in the Offspring. *Pediatrics* [Internet] 2014;133:e674-e688.

770 Driesche S van den, Macdonald J, Anderson RA, Johnston ZC, Chetty T, Smith LB, Mckinnell C, Dean A, Homer NZ, Jorgensen A, et al. Prolonged exposure to acetaminophen reduces testosterone production by the human fetal testis in a xenograft model. *Sci Transl Med* 2015;7:288ra80.

773 eurocat syndrome guide definition and coding of syndromes. *JRC-eurocat central registry.european surveillance of congenital anomalies. version july 2017:*

775 Eyers S, Weatherall M, Jefferies S, Beasley R. Paracetamol in pregnancy and the risk of wheezing in offspring: a systematic review and meta-analysis. *Clin Exp Allergy J Br Soc Allergy Clin Immunol* 2011;41:482-489. England.

778 Farquhar H, Stewart A, Mitchell E, Crane J, Eyers S, Weatherall M, Beasley R. The role of paracetamol in the pathogenesis of asthma. *Clin Exp Allergy J Br Soc Allergy Clin Immunol* 2010;40:32-41. England.

780 Feldkamp ML, Meyer RE, Krikov S, Botto LD. Acetaminophen Use in Pregnancy and Risk of Birth Defects: Findings From the National Birth Defects Prevention Study. *Obstet Gynecol* [Internet] 2010;115:109-115.
783 Fisher BG, Thankamony A, Hughes IA, Ong KK, Dunger DB, Acerini CL. Prenatal paracetamol exposure is associated with shorter anogenital distance in male infants. *Hum Reprod* [Internet] 2016;31:2642–2650.

785 Gaspari L, Paris F, Jandel C, Kalfa N, Orsini M, Daures JP, Sultan C. Prenatal environmental risk factors for genital malformations in a population of 1442 French male newborns: a nested case-control study. *Hum Reprod* [Internet] 2011;26:3155–3162.

788 Gonzalez A, Hinson D, Varney S, Maddry J. Acetaminophen overdose in a 720-gram, 25-week-gestation, five-day-old, micro-preemie. *Clin Toxicol* [Internet] 2020;58:1133–1134.

790 Gupta C, Goldman AS. The arachidonic acid cascade is involved in the masculinizing action of testosterone on embryonic external genitalia in mice. *Proc Natl Acad Sci* [Internet] 1986;83:4346–4349.

792 Gurney J, Richiardi L, McGlynn KA, Signal V, Sarfati D. Analgesia use during pregnancy and risk of cryptorchidism: a systematic review and meta-analysis. *Hum Reprod Oxf Engl* 2017;32:1118–1129.

794 Guyatt GH, Oxman AD, Vist GE, Kunz R, Falck-Ytter Y, Alonso-Coello P, Schünemann HJ, GRADE Working Group. GRADE: an emerging consensus on rating quality of evidence and strength of recommendations. *BMJ* 2008;336:924–926.

797 Higgins Jpt, Thomas J, Chandler J, Cumpston M, Li T, Page Mj, Welch Va. *Cochrane Handbook for Systematic Reviews of Interventions version 6.4 (updated August 2023)*. Cochrane, 2023. Available from www.training.cochrane.org/handbook. 2024;

800 Holm JB, Chalmey C, Modick H, Jensen LS, Dierkes G, Weiss T, Jensen BAH, Nørregård MM, Borkowski K, Styrishave B, et al. Aniline Is Rapidly Converted Into Paracetamol Impairing Male Reproductive Development. *Toxicol Sci* [Internet] 2015;148:288–298.

803 Hutson JM, Southwell BR, Li R, Lie G, Ismail K, Harisis G, Chen N. The regulation of testicular descent and the effects of cryptorchidism. *Endocr Rev* 2013;34:725–752.
805 Interrante JD, Ailes EC, Lind JN, Anderka M, Feldkamp ML, Werler MM, Taylor LG, Trinidad J, Gilboa SM, Broussard CS. Risk comparison for prenatal use of analgesics and selected birth defects, National Birth Defects Prevention Study 1997–2011. *Ann Epidemiol* [Internet] 2017;27:645-653.e2.

808 Jensen MS, Rebordosa C, Thulstrup AM, Toft G, Sørensen HT, Bonde JP, Henriksen TB, Olsen J. Maternal Use of Acetaminophen, Ibuprofen, and Acetylsalicylic Acid During Pregnancy and Risk of Cryptorchidism. *Epidemiology* [Internet] 2010;21:779-785.

811 Journal of Open Source Software: Welcome to the Tidyverse Available from: https://joss.theoj.org/papers/10.21105/joss.01686.

813 Kristensen DM, Hass U, Lesné L, Lottrup G, Jacobsen PR, Desdoits-Lethimonier C, Boberg J, Petersen JH, Toppari J, Jensen TK, et al. Intrauterine exposure to mild analgesics is a risk factor for development of male reproductive disorders in human and rat. *Hum Reprod* [Internet] 2011a;26:235-244.

816 Kristensen DM, Mazaud-Guittot S, Gaudriault P, Lesné L, Serrano T, Main KM, Jégou B. Analgesic use - prevalence, biomonitoring and endocrine and reproductive effects. *Nat Rev Endocrinol* 2016;12:381-393. England.

819 Kristensen DM, Skalkam ML, Audouze K, Lesné L, Desdoits-Lethimonier C, Frederiksen H, Brunak S, Skakkebæk NE, Jégou B, Hansen JB, et al. Many Putative Endocrine Disruptors Inhibit Prostaglandin Synthesis. *Environ Health Perspect* [Internet] 2011b;119:534-541.

822 Leslie SW, Sajjad H, Villanueva CA. Cryptorchidism. *StatPearls* [Internet] 2024; StatPearls Publishing: Treasure Island (FL) Available from: http://www.ncbi.nlm.nih.gov/books/NBK470270/.

824 Liew Z, Ritz B, Rebordosa C, Lee P-C, Olsen J. Acetaminophen use during pregnancy, behavioral problems, and hyperkinetic disorders. *JAMA Pediatr* 2014;168:313-320.

826 Lin L. Comparison of four heterogeneity measures for meta-analysis. *J Eval Clin Pract* [Internet] 2020;26:376-384.
828 Lind DV, Main KM, Kyhl HB, Kristensen DM, Toppari J, Andersen HR, Andersen MS, Skakkebæk NE, Jensen TK.

829 Maternal use of mild analgesics during pregnancy associated with reduced anogenital distance in sons:

830 a cohort study of 1027 mother–child pairs. *Hum Reprod* [Internet] 2016;humrep:dew285v1Available

831 from: https://academic.oup.com/humrep/article-lookup/doi/10.1093/humrep/dew285.

832 Lind JN, Tinker SC, Broussard CS, Reefhuis J, Carmichael SL, Honein MA, Olney RS, Parker SE, Werler MM, for

833 the National Birth Defects Prevention Study. Maternal medication and herbal use and risk for

834 hypospadias: data from the National Birth Defects Prevention Study, 1997–2007. *Pharmacoepidemiol*

835 *Drug Saf* [Internet] 2013;22:783–793.

836 Mazaud-Guittot S, Nicolaz CN, Desdoits-Lethimonier C, Coiffec I, Maamar MB, Balaguer P, Kristensen DM,

837 Chevrier C, Lavoué V, Poulain P, et al. Paracetamol, Aspirin, and Indomethacin Induce Endocrine

838 Disturbances in the Human Fetal Testis Capable of Interfering With Testicular Descent. *J Clin Endocrinol*

839 *Metab* [Internet] 2013;98:E1757–E1767.

840 McGuinness LA, Higgins JPT. Risk-of-bias VISualization (robvis): An R package and Shiny web app for

841 visualizing risk-of-bias assessments. *Res Synth Methods* [Internet] 2021;12:55–61.

842 McMaster University and Evidence Prime. GRADEpro GDT: GRADEpro Guideline Development ToolAvailable

843 from: https://www.gradepro.org/.

844 Moher D, Liberati A, Tetzlaff J, Altman DG, PRISMA Group. Preferred reporting items for systematic reviews and

845 meta-analyses: the PRISMA statement. *PLoS Med* 2009;6:e1000097.

846 Navarro-Lafuente F, Arense-Gonzalo J, Adoamnei E, Prieto-Sánchez M, Sánchez-Ferrer M, García-Marcos L,

847 Morales E, Mendiola J, Torres-Cantero A, the NELA Study Group. Is Maternal Use of Paracetamol

848 during Pregnancy Associated with Anogenital Distance in Male Newborns? The Results from the NELA

849 Birth Cohort. *Int J Environ Res Public Health* [Internet] 2021;18:6338.

850 Philibert P, Boizet-Bonhoure B, Bashamboo A, Paris F, Aritake K, Urade Y, Leger J, Sultan C, Poulat F. Unilateral

851 cryptorchidism in mice mutant for Ptgds. *Hum Mutat* 2013;34:278–282.
852 Philippa D.Darbre. Urogenital tract malformation. *Endocr Disrupt Male Reprod Health* 2015;, p. 164–165.

853 Elsevier.

854 Poletta FA, López Camelo JS, Gili JA, Leoncini E, Castilla EE, Mastroiacovo P. Methodological Approaches to

855 Evaluate Teratogenic Risk Using Birth Defect Registries: Advantages and Disadvantages. In Singh A,

856 editor. *PLoS ONE* [Internet] 2012;7:e46626.

857 R Core Team (2021). *R: A language and environment for statistical computing*. R Foundation for Statistical

858 Computing, Vienna, Austria. Available from: https://www.R-project.org/.

859 Rebordosa C, Kogevinas M, Horváth-Puhó E, Nørgård B, Morales M, Czeizel AE, Vilstrup H, Sørensen HT, Olsen

860 J. Acetaminophen use during pregnancy: effects on risk for congenital abnormalities. *Am J Obstet

861 *Gynecol* [Internet] 2008;198:178.e1-178.e7.

862 Rücker G, Schwarzer G, Schumacher M. Heterogeneity in meta-analysis: misconceiving I². In: Evidence in the

863 era of globalisation. Abstracts of the 16th Cochrane Colloquium; 2008 3-7 Oct; Freiburg, Germany.

864 2008. 2008;

865 Salazar-Martinez E, Romano-Riquer P, Yanez-Marquez E, Longnecker MP, Hernandez-Avila M. Anogenital

866 distance in human male and female newborns: a descriptive, cross-sectional study. *Environ Health

867 [Internet] 2004;3:8.

868 Sekaran P, O'Toole S, Flett M, Cascio S. Increased occurrence of disorders of sex development, prematurity and

869 intrauterine growth restriction in children with proximal hypospadias associated with undescended

870 testes. *J Urol* 2013;189:1892–1896.

871 Shan X, Aguilar S, Canon S. Hypospadias prevalence by severity and associated risk factors: A population-based

872 active surveillance analysis. *J Pediatr Urol* [Internet] 2023;19:e1-720.e9.

873 Sharpe RM. Androgens and the masculinization programming window: human-rodent differences. *Biochem Soc

874 *Trans* 2020;48:1725–1735.
875 Sharpe RM, Skakkebaek NE. Testicular dysgenesis syndrome: mechanistic insights and potential new
876 downstream effects. *Fertil Steril* [Internet] 2008;89:e33–e38.

877 Shen J, Cunha GR, Sinclair A, Cao M, Isaacson D, Baskin L. Macroscopic whole-mounts of the developing
878 human fetal urogenital-genital tract: Indifferent stage to male and female differentiation. *Differ Res Biol
879 Divers* 2018;103:5–13.

880 Snijder CA, Kortenkamp A, Steegers EAP, Jaddoe VWV, Hofman A, Hass U, Burdorf A. Intrauterine exposure to
881 mild analgesics during pregnancy and the occurrence of cryptorchidism and hypospadia in the offspring:
882 the Generation R Study. *Hum Reprod* [Internet] 2012;27:1191–1201.

883 Sterne JA, Hernán MA, Reeves BC, Savović J, Berkman ND, Viswanathan M, Henry D, Altman DG, Ansari MT,
884 Boutron I, et al. ROBINS-I: a tool for assessing risk of bias in non-randomised studies of interventions.
885 BMJ [Internet] 2016;i4919Available from: https://www.bmj.com/lookup/doi/10.1136/bmj.i4919.

886 Stroup DF, Berlin JA, Morton SC, Olkin I, Williamson GD, Rennie D, Moher D, Becker BJ, Sipe TA, Thacker SB.
887 Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis Of
888 Observational Studies in Epidemiology (MOOSE) group. *JAMA* 2000;**283**:2008–2012.

889 Tasian GE, Zaid H, Cabana MD, Baskin LS. Proximal hypospadias and risk of acquired cryptorchidism. *J Urol*
890 2010;**184**:715–720.

891 Thankamony A, Ong KK, Dunger DB, Acerini CL, Hughes IA. Anogenital distance from birth to 2 years: a
892 population study. *Environ Health Perspect* 2009;117:1786–1790.

893 VanderWeele TJ. Optimal approximate conversions of odds ratios and hazard ratios to risk ratios. *Biometrics*
894 [Internet] 2020;76:746–752.

895 Viechtbauer W. Conducting Meta-Analyses in R with the metafor Package. *J Stat Softw* [Internet] 2010;**36**:1–48.
896 Wang Y, Wang L, Yang Z, Chen F, Liu Z, Tang Z. Association between perinatal factors and hypospadias in newborns: a retrospective case-control study of 42,244 male infants. *BMC Pregnancy Childbirth* [Internet] 2022;22:579.

899 Weckman AM, Ngai M, Wright J, McDonald CR, Kain KC. The Impact of Infection in Pregnancy on Placental Vascular Development and Adverse Birth Outcomes. *Front Microbiol* [Internet] 2019;10:1924.

901 Welsh M, Saunders PTK, Fisken M, Scott HM, Hutchison GR, Smith LB, Sharpe RM. Identification in rats of a programming window for reproductive tract masculinization, disruption of which leads to hypospadias and cryptorchidism. *J Clin Invest* [Internet] 2008;118:1479-1490.

904 Wickham H, François R, Henry L, Müller K, Vaughan D. dplyr: A Grammar of Data Manipulation. 2024; tidyverseAvailable from: https://github.com/tidyverse/dplyr.

906 Wood HM, Elder JS. Cryptorchidism and testicular cancer: separating fact from fiction. *J Urol* 2009;181:452-461.

907 Ystrom E, Gustavson K, Brandlistuen RE, Knudsen GP, Magnus P, Susser E, Davey Smith G, Stoltenberg C, Surén P, Häberg SE, et al. Prenatal Exposure to Acetaminophen and Risk of ADHD. *Pediatrics* 2017;140:e20163840.

910 Zafeiri A, Mitchell RT, Hay DC, Fowler PA. Over-the-counter analgesics during pregnancy: a comprehensive review of global prevalence and offspring safety. *Hum Reprod Update* [Internet] 2021;27:67-95.

912 Zafeiri A, Raja EA, Mitchell RT, Hay DC, Bhattacharya S, Fowler PA. Maternal over-the-counter analgesics use during pregnancy and adverse perinatal outcomes: cohort study of 151 141 singleton pregnancies. *BMJ Open* [Internet] 2022;12:e048092.

915 Zotero | AboutAvailable from: https://www.zotero.org/about/.
<table><caption>Table 1: Characteristics of the included studies</caption><thead><tr><th>First author, year</th><th>Country</th><th>Inclusion period</th><th>Design</th><th>Population-based</th><th>Data Collection</th><th>Data sources</th><th>Number of offsprings</th><th>Acetaminophen exposure identification</th><th>Period of exposure (in Trimester or weeks of gestation)</th><th>Definition of comparison group</th><th>Reported outcomes</th><th>Definition of outcomes</th></tr></thead><tbody><tr><td>Rebordosa, 2008</td><td>Denmark</td><td>1996-2003</td><td>Retrospective Cohort</td><td>Yes</td><td>Prospective</td><td>Registry: DNBC*</td><td>Exposed: 26424; Unexposed: 61718</td><td>Self-reported use of paracetamol using auto questionnaire and 4 interviews†</td><td>T1</td><td>No medication</td><td>Cryptorchidism<br>Hypospadias</td><td>ICD-10 codes<br>EUROCAT</td></tr><tr><td>Jensen, 2010</td><td>Denmark</td><td>1996-2002</td><td>Retrospective Cohort</td><td>Yes</td><td>Prospective</td><td>Registry: DNBC*</td><td>Exposed: 22449; Unexposed: 21504</td><td>Self-reported use of paracetamol using auto questionnaire and 3 interviews†</td><td>T1; T2; T3; T1+T2; T2+T3; All 3 T</td><td>No medication</td><td>Cryptorchidism</td><td>ICD10 EUROCAT codes: Q53, Q531, Q531A, Q532, Q532A, and Q539.</td></tr><tr><td>Kristensen, 2011¶</td><td>Denmark - Finland</td><td>1997-2001¶</td><td>Prospective Cohort</td><td>No</td><td>Prospective</td><td>Chart review: University Hospital of Copenhagen</td><td>Exposed: 233; Unexposed: 257</td><td>Self-reported use of paracetamol using interview</td><td>Any T; T1; T2</td><td>No medication</td><td>Cryptorchidism</td><td>Cryptorchid testis: high scrotal, supra-scrotal, inguinal or non-palpable.</td></tr><tr><td>Poletta, 2012</td><td>Brazil - Argentina</td><td>1967-2008</td><td>Case - Control</td><td>Yes</td><td>Retrospective</td><td>Registry: ECLAMC†</td><td>Cases: 3390§</td><td>ATC code Acetaminophen: (N02BE01) ¥ using interviews</td><td>T1</td><td>No medication</td><td>Hypospadias°</td><td>ICD-10 codes</td></tr><tr><td>Snijder, 2012</td><td>Netherlands</td><td>2002-2006</td><td>Retrospective Cohort</td><td>Yes</td><td>Prospective</td><td>Registry: Municipal birth register</td><td>Exposed: 1st period 184 - 2nd period: 465 - 3rd period: 349; Unexposed: 1st period: 68 - 2nd period: 15 - 3rd period: 14</td><td>Self-reported use of paracetamol as OTC using 4 auto questionnaire</td><td>Preconception period; 0-14 weeks; 14-22 weeks; 20-32 weeks</td><td>Other painkillers including NSAIDS, aspirin</td><td>Cryptorchidism<br>Hypospadias</td><td>Cryptorchidism: one or both testes nonpalpable, or not into a stable position in the scrotum;<br>Hypospadias: as described by Pierik et al. (2002)</td></tr><tr><td>Fisher, 2016</td><td>United Kingdom</td><td>2001-2009</td><td>Prospective Cohort</td><td>No</td><td>Prospective</td><td>Chart review: Rosie Maternity Unit, Addenbrooke's Hospital, Cambridge</td><td>Exposed male: 225; Exposed female: 148; Unexposed male: 456; Unexposed female: 253</td><td>Self-reported use of 'paracetamol', 'co-codamol', 'co-dydramol' or 'acetaminophen'</td><td>Any T</td><td>No medication</td><td>Cryptorchidism</td><td>One or more testes not present in the inferior half of the scrotum few moments after manipulation</td></tr></tbody></table>
<table><tr><td>Zafeiri, 2022</td><td>United Kingdom</td><td>1985-2015</td><td>Retrospective Cohort</td><td>Yes</td><td>Retrospective</td><td>Registry: AMND§ and chart review from the Aberdeen Maternity Hospital</td><td>Exposed: 24099; Non-Exposed: 107143</td><td>Self-reported use of paracetamol as OTC or prescribed medication using medical charts</td><td>Any T</td><td>No medications</td><td>Cryptorchidism</td><td>ICD10code Q53</td></tr><tr><td colspan="12"></td><td>Hypospadias</td><td>ICD10code Q54</td></tr></table>

† Acetaminophen alone or combined with other painkillers including both prescribed and over the counter medications.

¶ Inclusion period in Denmark. Only data from the Danish cohort were considered since the use of acetaminophen was not reported in the Finish cohort.

¥ Acetaminophen with or without other medications.

° Birth defect isolated or combined with other anomalies.

ψ Birth defect cases among live born, stillborn, and induced abortions.

§ Number of controls not reported.

AGD: Anogenital distance, AMND Neonatal Databank in Aberdeen, DNBC: Danish national birth cohort, ECLAM: Latin American Collaborative Study of Congenital Anomalies, EUROCAT: European registration of congenital anomalies and twins, ICD: International Statistical Classification of Diseases, NBDPS: National Birth Defects Prevention Study, OTC: over the counter, T: trimester, T1: first trimester, T2: second trimester, T3: third trimester, USA: United States of America.
<table><caption>Table 2: GRADE assessment for associations between in utero exposure to Acetaminophen and external genital tract malformations in boys.</caption><thead><tr><th rowspan="2"></th><th colspan="3">Anticipated absolute effects (95% CI)</th><th rowspan="2"></th></tr><tr><th>No medications</th><th>Acetaminophen</th><th>Difference</th></tr></thead><tbody><tr><td>composite outcome:<br>hypospadias and / or<br>cryptorchidism<br>Nº of participants: 155362<br>(2 non-randomised studies)</td><td>OR 1.27<br>(0.18 to 8.94)</td><td>0.7%</td><td>0.9%<br>(0.1 to 6.2)</td><td><strong>0.2% more</strong><br>(0.6 fewer to 5.5<br>more)<br>⊕○○○<br>Very low<sup>a,b,c</sup></td><td>The evidence is very uncertain about the effect of<br>acetaminophen on composite outcome:<br>hypospadias and / or cryptorchidism.</td></tr><tr><td>cryptorchidism<br>assessed with: OR<br>Nº of participants: 155852<br>(3 non-randomised studies)</td><td>OR 1.02<br>(0.78 to 1.35)</td><td>0.4%</td><td>0.4%<br>(0.3 to 0.5)</td><td><strong>0.0% fewer</strong><br>(0.1 fewer to 0.1<br>more)<br>⊕○○○<br>Very low<sup>c,d</sup></td><td>The evidence is very uncertain about the effect of<br>acetaminophen on cryptorchidism.</td></tr><tr><td>hypospadias<br>assessed with: OR<br>Nº of participants: 159572<br>(3 non-randomised studies)</td><td>OR 1.02<br>(0.89 to 1.17)</td><td>0.7%</td><td>0.7%<br>(0.7 to 0.9)</td><td><strong>0.0% fewer</strong><br>(0.1 fewer to 0.1<br>more)<br>⊕⊕○○<br>Low<sup>e</sup></td><td>The evidence suggests that acetaminophen does<br>not increase hypospadias.</td></tr><tr><td>Anogenital distance<br>assessed with: mean difference<br>Nº of participants: 958<br>(2 non-randomised studies)</td><td>-</td><td>The mean anogenital distance difference was 0 cm</td><td>-</td><td>MD 0 cm<br>(0.07 lower to 0.08<br>higher)<br>⊕○○○<br>Very low<sup>c,f</sup></td><td>The evidence is very uncertain about the effect of<br>acetaminophen on anogenital distance.</td></tr></tbody></table>

Patient or population: foetus, embryo, newborn, children

Setting: pregnancy and neonatal period

Intervention: in utero exposure to acetaminophen

Comparison: in utero exposure to no medications
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).

CI: confidence interval; MD: mean difference; OR: odds ratio

**GRADE Working Group grades of evidence**

Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect.

Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

**Explanations**

a. No adjusted analysis for the composite outcome as it was reconstructed from 2 studies.

b. High heterogeneity, I2= 79%

c. Wide confidence interval, no enough information for potential important harm or benefit

d. Risk of bias was serious for 2 studies and critical for 1 study according to ROBINS-I.

e. Risk of bias was serious in the 3 included studies according to ROBINS-I

f. Risk of bias was critical for the 2 included studies according to ROBINS-I
<figure><img src="image_3.png" /><figcaption>Identification of new studies via other methods</figcaption></figure>

<figure><img src="image_4.png" /></figure>
<table><thead><tr><th>Study</th><th>D1</th><th>D2</th><th>D3</th><th>D4</th><th>D5</th><th>D6</th><th>D7</th><th>Overall</th></tr></thead><tbody><tr><td>Zafeiri, 2022</td><td>X</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>X</td></tr><tr><td>Navarro-Lafuente, 2021</td><td>!</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>!</td></tr><tr><td>Lind, 2017</td><td>X</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>●</td><td>X</td></tr><tr><td>Interrante, 2017</td><td>X</td><td>+</td><td>-</td><td>+</td><td>+</td><td>+</td><td>+</td><td>X</td></tr><tr><td>Fisher, 2016</td><td>!</td><td>+</td><td>+</td><td>+</td><td>-</td><td>+</td><td>●</td><td>!</td></tr><tr><td>Poletta, 2012</td><td>!</td><td>X</td><td>-</td><td>+</td><td>+</td><td>+</td><td>X</td><td>!</td></tr><tr><td>Snijder, 2012</td><td>X</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>-</td><td>X</td></tr><tr><td>Kristensen, 2011</td><td>!</td><td>+</td><td>+</td><td>+</td><td>X</td><td>+</td><td>+</td><td>!</td></tr><tr><td>Jensen, 2010</td><td>X</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>●</td><td>X</td></tr><tr><td>Rebordosa, 2008</td><td>X</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>+</td><td>X</td></tr></tbody></table>

Domains:

D1: Bias due to confounding.

D2: Bias due to selection of participants.

D3: Bias in classification of interventions.

D4: Bias due to deviations from intended interventions.

D5: Bias due to missing data.

D6: Bias in measurement of outcomes.

D7: Bias in selection of the reported result.

Judgement

<figure><img src="image_5.png" /></figure>

Low risk

<figure><img src="image_6.png" /></figure>

Moderate risk

<figure><img src="image_7.png" /></figure>

Serious risk

<figure><img src="image_8.png" /></figure>

Critical risk

<figure><img src="image_9.png" /></figure>

No information
a

Meta-analysis of the composite outcome

<figure><img src="image_10.png" /></figure>

b

Meta-analysis for cryptorchidism

<figure><img src="image_11.png" /></figure>

C

Meta-analysis for hypospadias

<figure><img src="image_12.png" /></figure>
a

Meta-analysis for anogenital distance in boys

<figure><img src="image_13.png" /></figure>

b

Meta-analysis for anogenital distance in boys using adjusted mean difference

<figure><img src="image_14.png" /></figure>

Heterogeneity: *I*² = 0%, *τ*² = 0, *p* = 0.86

c

Meta-analysis for anogenital distance in boys exposed in the first trimester

<figure><img src="image_15.png" /></figure>

Heterogeneity: *I*² = 43%, *τ*² = 0.0085, *p* = 0.19

d

Meta-analysis for anogenital distance in boys exposed in the second trimester

<figure><img src="image_16.png" /></figure>

Heterogeneity: *I*² = 0%, *τ*² = 0, *p* = 0.85
Meta-analysis of the composite outcome using fixed and random effects models

<table><thead><tr><th>Study</th><th>Exposed<br>(events/total)</th><th>Unexposed<br>(events/total)</th><th>Risk of Bias</th><th>Odds ratio(crude)</th><th>OR</th><th>95%-CI</th><th>Weight (fixed)</th><th>Weight(random)</th></tr></thead><tbody><tr><td>Rebordosa, 2008</td><td>113 / 26424</td><td>244 / 61718</td><td>Serious</td><td></td><td>1.08</td><td>[0.87; 1.35]</td><td>39.5%</td><td>46.6%</td></tr><tr><td>Zafeiri, 2022</td><td>203 / 12354</td><td>616 / 54866</td><td>Serious</td><td></td><td>1.47</td><td>[1.25; 1.73]</td><td>60.5%</td><td>53.4%</td></tr><tr><td>Fixed effect model</td><td></td><td></td><td></td><td></td><td><strong>1.32</strong></td><td>[1.16; 1.50]</td><td><strong>100.0%</strong></td><td></td></tr><tr><td>Random effects model</td><td></td><td></td><td></td><td></td><td><strong>1.27</strong></td><td>[0.18; 8.94]</td><td></td><td><strong>100.0%</strong></td></tr></tbody></table><p>Heterogeneity: I<sup>2</sup> = 79.2%, τ<sup>2</sup> = 0.0374, p = 0.0284</p>

<figure><img src="image_17.png" /></figure>
<figure><img src="image_18.png" /><figcaption>Fig. S1: Meta-analysis for cryptorchidism after exposure to acetaminophen at any time during pregnancy using crude odds ratios</figcaption></figure>

CI: confidence interval, OR: odds ratio

<figure><img src="image_19.png" /><figcaption>Fig. S2: Sensitivity analysis for cryptorchidism excluding studies reporting the use of acetaminophen combined with other pain killers</figcaption></figure>

CI: confidence interval, OR: odds ratio

<figure><img src="image_20.png" /><figcaption>Fig. S3: Sensitivity analysis for cryptorchidism including studies with a serious risk of bias only</figcaption></figure>

CI: confidence interval, OR: odds ratio
<figure><img src="image_21.png" /><figcaption>Fig. S4: Meta-analysis for hypospadias after exposure to acetaminophen at any time during pregnancy using crude odds ratios</figcaption></figure>

CI: confidence interval, OR: odds ratio

<figure><img src="image_22.png" /><figcaption>Fig. S5: Sensitivity analysis for hypospadias after exposure to acetaminophen at any time during pregnancy excluding studies reporting the use of acetaminophen combined with other pain killers</figcaption></figure>

CI: confidence interval, OR: odds ratio

<figure><img src="image_23.png" /><figcaption>Fig. S6: Sensitivity analysis for hypospadias including studies that only have live births after exposure to acetaminophen at any time during pregnancy</figcaption></figure>

CI: confidence interval, OR: odds ratio
<table><caption>Fig. S7: Meta-analysis for cryptorchidism after exposure in the first trimester using adjusted odds ratios</caption><thead><tr><th>Study</th><th>Exposed (events/total)</th><th>Unexposed (events/total)</th><th>Risk of Bias</th><th>Odds ratio(adjusted)</th><th>OR</th><th>95%-CI</th><th>Weight (fixed)</th><th>Weight(random)</th></tr></thead><tbody><tr><td>Jensen, 2010</td><td>92 / 22449</td><td>480 / 21504</td><td>serious</td><td></td><td>0.94</td><td>[0.75; 1.18]</td><td>89.1%</td><td>89.1%</td></tr><tr><td>Kristensen, 2011</td><td>7 / 56</td><td>29 / 342</td><td>serious</td><td></td><td>1.54</td><td>[0.63; 3.74]</td><td>5.9%</td><td>5.9%</td></tr><tr><td>Snijder, 2012</td><td>5 / 184</td><td>0 / 68</td><td>serious</td><td></td><td>1.38</td><td>[0.52; 3.65]</td><td>4.9%</td><td>4.9%</td></tr><tr><td colspan="9"><strong>Fixed effect model</strong></td></tr><tr><td colspan="9"><strong>Random effects model</strong></td></tr><tr><td colspan="9">Heterogeneity: I<sup>2</sup> = 0%, τ<sup>2</sup> = 0, p = 0.45</td></tr></tbody></table>

CI: confidence interval, OR: odds ratio

<table><caption>Fig. S8: Meta-analysis for cryptorchidism after exposure in the first trimester using crude odds ratios</caption><thead><tr><th>Study</th><th>Exposed (events/total)</th><th>Unexposed (events/total)</th><th>Risk of Bias</th><th>Odds ratio(crude)</th><th>OR</th><th>95%-CI</th><th>Weight (fixed)</th><th>Weight(random)</th></tr></thead><tbody><tr><td>Kristensen, 2011</td><td>7 / 56</td><td>29 / 342</td><td>serious</td><td></td><td>1.54</td><td>[0.64; 3.71]</td><td>53.6%</td><td>53.6%</td></tr><tr><td>Snijder, 2012</td><td>5 / 184</td><td>0 / 68</td><td>serious</td><td></td><td>1.34</td><td>[0.52; 3.45]</td><td>46.4%</td><td>46.4%</td></tr><tr><td colspan="9"><strong>Fixed effect model</strong></td></tr><tr><td colspan="9"><strong>Random effects model</strong></td></tr><tr><td colspan="9">Heterogeneity: I<sup>2</sup> = 0%, τ<sup>2</sup> = 0, p = 0.83</td></tr></tbody></table>

CI: confidence interval, OR: odds ratio

<table><caption>Fig. S9: Meta-analysis for cryptorchidism after exposure in the second trimester using adjusted odds ratios</caption><thead><tr><th>Study</th><th>Exposed (events/total)</th><th>Unexposed (events/total)</th><th>Risk of Bias</th><th>Odds ratio(adjusted)</th><th>OR</th><th>95%-CI</th><th>Weight (fixed)</th><th>Weight(random)</th></tr></thead><tbody><tr><td>Jensen, 2010</td><td>58 / 22449</td><td>480 / 21504</td><td>serious</td><td></td><td>1.17</td><td>[0.89; 1.54]</td><td>87.9%</td><td>74.5%</td></tr><tr><td>Kristensen, 2011</td><td>13 / 95</td><td>23 / 303</td><td>serious</td><td></td><td>1.93</td><td>[0.92; 4.04]</td><td>12.1%</td><td>25.5%</td></tr><tr><td colspan="9"><strong>Fixed effect model</strong></td></tr><tr><td colspan="9"><strong>Random effects model</strong></td></tr><tr><td colspan="9">Heterogeneity: I<sup>2</sup> = 35%, τ<sup>2</sup> = 0.0444, p = 0.21</td></tr></tbody></table>

CI: confidence interval, OR: odds ratio
<table><caption>Fig. S10: Subgroup analysis according to risk of bias for cryptorchidism using adjusted odds ratios</caption><thead><tr><th>Study</th><th>Exposed<br>(events/total)</th><th>Unexposed<br>(events/total)</th><th>Risk of Bias</th><th>Odds Ratio</th><th>OR</th><th>95%-CI</th><th>Weight (fixed)</th><th>Weight(random)</th></tr></thead><tbody><tr><td><strong>Risk of bias: Serious</strong><br>Rebordosa, 2008<br>33 / 26424<br>63 / 61718<br>Serious</td><td></td><td></td><td></td><td></td><td>1.24 [0.79; 1.94]</td><td></td><td>18.7%</td><td>27.1%</td></tr><tr><td>Zafeiri, 2022<br>107 / 12354<br>357 / 54866<br>Serious</td><td></td><td></td><td></td><td></td><td>0.87 [0.69; 1.09]</td><td></td><td>72.2%</td><td>57.5%</td></tr><tr><td><strong>Fixed-effect model</strong><br>Random-effect model<br>Heterogeneity: I<sup>2</sup> = 47%, t<sup>2</sup> = 0.0297, p = 0.17</td><td></td><td></td><td></td><td></td><td>0.94 [0.76; 1.15]</td><td></td><td>91.0%</td><td></td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>0.98 [0.71; 1.37]</td><td></td><td>.</td><td>84.6%</td></tr><tr><td><strong>Risk of bias: Critical</strong><br>Kristensen, 2011<br>23 / 233<br>19 / 257<br>Critical</td><td></td><td></td><td></td><td></td><td>1.33 [0.70; 2.54]</td><td></td><td>9.0%</td><td>15.4%</td></tr><tr><td><strong>Fixed-effect model</strong><br>Random-effect model<br>Heterogeneity: I<sup>2</sup> = 32%, t<sup>2</sup> = 0.0211, p = 0.23<br>Test for subgroup differences (common effect): χ<sup>2</sup> = 1.03, df = 1 (p = 0.31)<br>Test for subgroup differences (random effects): χ<sup>2</sup> = 0.67, df = 1 (p = 0.41)</td><td></td><td></td><td></td><td></td><td>0.97 [0.80; 1.17]</td><td></td><td>100.0%</td><td></td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>1.02 [0.78; 1.35]</td><td></td><td>.</td><td>100.0%</td></tr></tbody></table>

<figure><img src="image_24.png" /></figure>

CI: confidence interval, OR: odds ratio

<table><caption>Fig. S11: Subgroup analysis according to risk of bias for hypospadias using crude odds ratios</caption><thead><tr><th>Study</th><th>Exposed<br>(events/total)</th><th>Unexposed<br>(events/total)</th><th>Risk of Bias</th><th>Odds Ratio (crude)</th><th>OR</th><th>95%-CI</th><th>Weight (fixed)</th><th>Weight(random)</th></tr></thead><tbody><tr><td><strong>Risk of bias: Critical</strong><br>Poletta, 2012<br>Critical</td><td></td><td></td><td></td><td></td><td>3.50 [2.58; 4.76]</td><td></td><td>13.8%</td><td>32.4%</td></tr><tr><td><strong>Risk of bias: Serious</strong><br>Interrante, 2017<br>2704 / 2704<br>424 / 1506<br>Serious</td><td></td><td></td><td></td><td></td><td>1.00 [0.87; 1.15]</td><td></td><td>62.5%</td><td>34.2%</td></tr><tr><td>Zafeiri, 2022<br>12354 / 12354<br>259 / 54866<br>Serious</td><td></td><td></td><td></td><td></td><td>1.65 [1.31; 2.08]</td><td></td><td>23.7%</td><td>33.4%</td></tr><tr><td><strong>Fixed-effect model</strong><br>Random-effect model<br>Heterogeneity: I<sup>2</sup> = 92%, t<sup>2</sup> = 0.1156, p < 0.01</td><td></td><td></td><td></td><td></td><td>1.15 [1.02; 1.30]</td><td></td><td>86.2%</td><td></td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>1.27 [0.78; 2.08]</td><td></td><td>.</td><td>67.6%</td></tr><tr><td><strong>Fixed-effect model</strong><br>Random-effect model<br>Heterogeneity: I<sup>2</sup> = 96%, t<sup>2</sup> = 0.3446, p < 0.01<br>Test for subgroup differences (common effect): χ<sup>2</sup> = 43.83, df = 1 (p < 0.01)<br>Test for subgroup differences (random effects): χ<sup>2</sup> = 11.74, df = 1 (p < 0.01)</td><td></td><td></td><td></td><td></td><td>1.34 [1.19; 1.50]</td><td></td><td>100.0%</td><td></td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>1.77 [0.90; 3.50]</td><td></td><td>.</td><td>100.0%</td></tr></tbody></table>

<figure><img src="image_25.png" /></figure>

CI: confidence interval, OR: odds ratio
<table><caption>Supplementary Table S1: Population characteristics from included studies</caption><thead><tr><th>Author, year</th><th>Study groups (n)</th><th>Maternal age (years)</th><th>Parity</th><th>Gestational age mean ± SD/ categorical n (%)</th><th>Birth weight(g)</th><th>Low birth weight¶</th><th>Indication for acetaminophen</th><th>BMI (kg/m2)</th><th>Diabetes</th><th>Hypertensive disorders</th><th>Smoking N (%) or median [IQR]</th><th>Alcohol</th><th>Other congenital malformations</th><th>Other medication exposure</th></tr><tr><th></th><th></th><th>mean ± SD/ categorical n (%)</th><th>n(%) primi / multi(%) or median [IQR]</th><th>preterm§</th><th>Mean ± SD</th><th>N (%)</th><th>category n</th><th>median [IQR]/categories n (%)</th><th>N (%)</th><th>N (%)</th><th>N (%)</th><th>N (%)</th><th>N (%)</th><th>yes/no or n (%)</th></tr></thead><tbody><tr><td rowspan="2">Rebordos et al, 2008</td><td>Exposed (26424)</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td>Unexposed (61718)</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td rowspan="2">Jensen et al, 2010</td><td>Exposed (22449)</td><td>&lt;35y (85.2); ≥35y (14.8)</td><td>primi: 9451 (42.1)</td><td>preterm: 965 (4.3)</td><td>NA</td><td>583 (2.6)</td><td>fever: 7453, joint pain: 4489, inflammation: 3726</td><td>NA</td><td>336 (1.5)•</td><td>NA</td><td>6555 (29.2)</td><td>NA</td><td>1571 (6.5)</td><td>NA</td></tr><tr><td>Unexposed (21504)</td><td>&lt;35y (85.5); ≥35y (14.5)</td><td>primi: 10364 (48.2)</td><td>preterm: 1118 (5.2)</td><td>NA</td><td>666 (3.1)</td><td>fever: 4558, joint pain: 2881, inflammation: 2365</td><td>NA</td><td>279 (1.3)•</td><td>NA</td><td>4946 (23.0)</td><td>NA</td><td>1397 (7.0)</td><td>NA</td></tr><tr><td rowspan="2">Kristensen et al, 2011</td><td>Exposed (233)</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td>Unexposed (257)</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td rowspan="2">Poletta et al, 2012</td><td>Cases (3390)</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td>Control</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td rowspan="2">Snijder et al, 2012</td><td>Exposed (by period: 1st: 184, 2nd: 465, 3rd: 349)</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td>Unexposed (by period: 1st: 68, 2nd: 15, 3rd: 14)</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr></tbody></table>
<table><tbody><tr><td rowspan="2">Fisher et al, 2016</td><td>Exposed<br>(male: 225,<br>female:<br>148)</td><td>33.5 ± 3.9</td><td>primi: 92 (42.4);<br>multi: 37(57.6)</td><td>male: 39.8 ±<br>1.3;<br>female: 40.1<br>± 1.2</td><td>male: 3560<br>± 480;<br>female:<br>3450 ± 440</td><td>NA</td><td>migraine: 133;<br>infection: 41;<br>nonspecific pain: 42;<br>joint: 13</td><td>23.5 [21.5,<br>26.0]</td><td>NA</td><td>NA</td><td>8 [3.6]</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td>Unexposed<br>(male: 456,<br>female:<br>253)</td><td>33.5 ± 3.9</td><td>primi: 184<br>(44.5); multi:<br>67(55.5)</td><td>male: 39.8 ±<br>1.7;<br>female: 39.7<br>± 1.6</td><td>male: 3580<br>± 550;<br>female:<br>3360 ± 560</td><td>NA</td><td></td><td></td><td>22.8 [20.9,26]</td><td>NA</td><td>NA</td><td>14<br>[3.1]</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td rowspan="2">Lind et al, 2016</td><td>Exposed<br>(male: 217,<br>female:<br>195)</td><td>30.8</td><td>primi: 193<br>(53.2); multi:<br>171 (46.8)</td><td>39.8;<br>preterm: 20<br>(5.6)</td><td>3490</td><td>NA</td><td>headache: 287;<br>migraine: 28;<br>influenza/cold: 214;<br>joint pain: 87</td><td>&lt;30: 310<br>(84.9);<br>≥30: 55 (15.1)</td><td>NA</td><td>NA</td><td>10<br>(2.8)</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td>Unexposed<br>(male: 342,<br>Female:<br>375)</td><td>30.9</td><td>primi: 370<br>(60.0); multi:<br>247 (40.0)</td><td>40; preterm:<br>22 (3.6)</td><td>3531</td><td>NA</td><td>headache: 182;<br>migraine: 10;<br>influenza/cold: 251;<br>joint pain: 120</td><td>&lt;30: 557<br>(90.4);<br>≥30:60 (9.6)</td><td>NA</td><td>NA</td><td>14<br>(2.3)</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td rowspan="2">Interrant<br>e et al, 2017</td><td>Cases<br>(1207)</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td>Controls<br>(3003)¥</td><td>27.7 ± 5.9</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>&lt;30: 2528<br>(78.3);<br>≥30: 609<br>(18.9)</td><td>NA</td><td>NA</td><td>593<br>(18.4)</td><td>1217<br>(37.7)</td><td>NA</td><td>Antibiotics: 350<br>(10.8)</td></tr><tr><td rowspan="2">Navarro-<br>lafuente<br>et al, 2021</td><td>Exposed<br>(171)</td><td>32.7 ± 4.3</td><td>previous<br>gestations: 1.1<br>± 1.2</td><td>NA</td><td>3288 ±<br>470.6</td><td>NA</td><td>NA</td><td>&lt;30: 152<br>(89.4);<br>≥30: 18 (10.6)</td><td>16 (9.4)°</td><td>6 (3.5)†;<br>1 (0.6)</td><td>23<br>(13.5)</td><td>13 (7.6)</td><td>NA</td><td>NA</td></tr><tr><td>Unexposed<br>(106)</td><td>33 ± 4.6</td><td>previous<br>gestations: 0.8<br>± 1</td><td>NA</td><td>3268 ±<br>458.8</td><td>NA</td><td>NA</td><td>&lt;30: 102<br>(96.2);<br>≥30: 4 (3.8)</td><td>10 (9.4)°</td><td>2 (1.9)†;<br>1(1)</td><td>15<br>(14.2)</td><td>7 (6.6)</td><td>NA</td><td>NA</td></tr><tr><td>Zafeiri et<br>al, 2022</td><td>Exposed<br>(24099)</td><td>&lt;35y: 21764<br>(90.3);<br>≥35y: 2335<br>(9.7)</td><td>primi: 1250<br>(51.9);<br>multi: 11587<br>(48.1)</td><td>preterm:<br>2510 (10.4)</td><td>NA</td><td>NA</td><td>NA</td><td>&lt;30: 16764<br>(80.7);<br>≥30: 3995<br>(19.2)</td><td></td><td>5461<br>(22.7)‡</td><td>5921<br>(25.1)</td><td>NA</td><td>neural tube<br>defect: 22<br>(0.1);<br>amniotic<br>band</td><td>NA</td></tr></tbody></table>
Association between in utero exposure to paracetamol (Acetaminophen) and external genital tract malformations in boys and girls: a systematic review and meta-analysis.

To enable PROSPERO to focus on COVID-19 submissions, this registration record has undergone basic automated checks for eligibility and is published exactly as submitted. PROSPERO has never provided peer review, and usual checking by the PROSPERO team does not endorse content. Therefore, automatically published records should be treated as any other PROSPERO registration. Further detail is provided here.

## Citation

Lina Eletri, Kristen Joseph-Delaffon, Benoit Marin, Delphine Mitanchez, Agnes Dechartres. Association between in utero exposure to paracetamol (Acetaminophen) and external genital tract malformations in boys and girls: a systematic review and meta-analysis. PROSPERO 2024 CRD42024536483 Available from: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42024536483

## Review question

To investigate the association between exposure to paracetamol during pregnancy and:

- the occurrence of external genital tract malformations in boys and girls separately, based on the EUROCAT classification for minor and major malformations, defined as the composite occurrence of cryptorchidism, hypospadias and penile hypoplasia in boys or in girls, enlargement of clitoris, fusion of labia, congenital malformations of vulva and congenital rectovaginal fistula. We selected these outcomes based on prevalence and clinical relevance in the neonatal period.

- the occurrence of all individual components of the composite outcome in male and female offspring separately.

- the mean difference in anogenital distance in male and female offspring.

## Searches

The following electronic databases will be searched:

- MEDLINE via PubMed, search date: 18/04/2024

- EMBASE, search date: 18/04/2024

- Cochrane database of systematic reviews, search date: 18/04/2024

- Cochrane Central Register of Controlled Trials (CENTRAL), search date: 18/04/2024

- The WHO International Clinical Trials Registry Platform (ICTRP), search date: 19/04/2024

- ClinicalTrials.gov, search date: 19/04/2024

- Specialized databases Reptox, Shepard's, and TERIS: search date: 19/04/2024

A search for abstracts from main international meetings in the field for the last 5 years.

Reference lists from all systematic reviews and selected studies.
Following the completion of the initial screening, a Teratology Information Service (TIS) expert and a clinical pharmacology expert will be asked to assess the list of included articles for completeness and add articles if needed.

Publication dates and languages will not be limited.

## Types of study to be included

Reports of randomized controlled trials (RCTs) and prospective and retrospective comparative observational studies (cohort and case-control studies) focusing on the association between in utero exposure to paracetamol and outcomes listed below will be included.

Systematic reviews and meta-analyses will not be included but their references will be examined. Expert opinions, editorials, letters, case series and preclinical research studies will not be included.

## Condition or domain being studied

In utero exposure to Paracetamol (Acetaminophen)

## Participants/population

The population of interest is all embryos/fetuses/newborns/children exposed in utero to paracetamol.

## Intervention(s), exposure(s)

Paracetamol (Acetaminophen) exposure during pregnancy.

## Comparator(s)/control

Embryos/fetuses/newborns/children not exposed in utero to paracetamol including those exposed to other medications.

## Context

Paracetamol is currently one of the most commonly used over the counter drugs worldwide. Globally, the use of paracetamol is becoming increasingly prevalent and estimated to be around 50% among pregnant women, and despite being deemed low risk by the FDA and EMA, concerns have been raised as research showed transplacental passage of paracetamol and its metabolites. Indeed, epidemiologic and preclinical studies have shown that prenatal exposure to paracetamol may increase the risk of neurodevelopmental disorders, wheezing and asthma. Observational studies have investigated the association between the exposure to paracetamol during pregnancy and the occurrence of urogenital malformations and reproductive disorders including hypospadias, undescended testes and an abnormal anogenital distance. Despite emerging concerns about an association between the use of paracetamol during pregnancy and developmental outcomes of the endocrine, reproductive, and urogenital systems in both sexes, only one meta-analysis was published by Gurney et al, on the association between prenatal use of analgesia (without regard to the type of medication) and cryptorchidism, where a weak association was found between the use of analgesia during pregnancy and the risk of cryptorchidism. Finally, given the lack of restriction on the consumption of paracetamol and given the increased prevalence of urogenital and reproductive disorders, a consensus statement was published calling for precautionary action regarding the use of paracetamol. Therefore, there is a need to thoroughly investigate the association between paracetamol during pregnancy and the occurrence of external genital tract malformations in the offspring in both sexes through a systematic review and meta-analysis.

## Main outcome(s)

The occurrence of external genital tract malformations based on the EUROCAT classification for minor and major malformations in boys and girls separately, and defined as the composite occurrence of cryptorchidism, hypospadias and penile hypoplasia in boys or enlargement of clitoris, fusion of labia, congenital malformations of vulva and congenital
rectovaginal fistula in girls.

We selected these outcomes based on prevalence and clinical relevance in the neonatal period.

## Additional outcome(s)

- The occurrence of cryptorchidism in male offspring.

- The occurrence of hypospadias in male offspring.

- The occurrence of penile hypoplasia in male offspring.

- The occurrence of enlargement of clitoris in female offspring.

- The occurrence of fusion of labia in female offspring.

- The occurrence of congenital recto-vaginal fistula in female offspring.

- The occurrence of congenital malformations of vulva in female offspring.

- The mean difference of the anogenital distance in boys and girls separately following their exposure in utero to paracetamol: defined as the distance from the anus to the genitals. This measurement is clinically defined as the distance between the center of anus to the base of scrotum in boys and from the center of anus to the posterior convergence of the fourchette (where the vestibule begins) in girls.

## Data extraction (selection and coding)

Retrieved records will be managed using Zotero v6.030 and duplicates will be removed.

One author (pediatrician) will first identify eligible studies by screening titles and abstracts who will then, along with a second author, independently read full texts to check for their eligibility. All disagreements will be resolved by discussion with the assistance of two other reviewers (an epidemiology expert and a neonatology expert) to reach consensus.

Two authors will independently extract data from included studies using a standardized data extraction grid. All disagreements will be resolved as stated above.

In case of missing or unclear data in the manuscript, we will attempt to contact the study authors.

Data listed below will be collected:

- General characteristics of the study

- Study design, sample selection, source of data, and sample size

- Population characteristics:

Maternal characteristics: maternal age, BMI, parity, obstetrical history, maternal medical history, personal or family history of genetic disorders or congenital birth defects, use of co medications, smoking and alcohol exposure.

Neonatal characteristics: gestational age, birth weight, primary and secondary outcomes listed above, method of outcome measurement, timing of outcome measurement, other congenital malformations, genetic diseases.
- In the exposure group: paracetamol, reason of prescription, dose during pregnancy, treatment duration and term of exposure, method of exposure measurement

- In the control group: no treatment, or other medications, method of exposure measurement in case of exposure to other medications

Results: number of participants, number of events for each outcome, crude and adjusted estimates between exposure and outcomes as well as 95% CI. Primary outcome measure: the composite criterion will be reconstructed after data extraction and collection following contact with the authors.

We will collect pregnancy outcomes if available. For continuous variable mean differences will be collected. Reported confounding factors will also be collected

Risk of bias (quality) assessment

The risk of bias will be independently assessed by two review authors with the updated versions of Cochrane Risk-of-Bias tool for Randomized Trials (RoB 2) for RCTs and the Non-Randomized Studies of Interventions (ROBINS-I) for non-randomized studies.

The assessment of bias will be performed focusing on the primary outcome. In cases where the primary outcome is not assessed, bias will be evaluated for each separate outcome.

All disagreements will be resolved by discussion with the help of two other reviewers (an epidemiology expert and a neonatology expert) to reach consensus.

Strategy for data synthesis

For binary outcomes, measures of association will be estimated using odds-ratios (OR).

Measures of association given in relative risks (RRs) only, will be considered equivalent to OR as all the outcomes are rare.

For continuous outcomes (anogenital distance), mean difference (MD) will be used.

Separate meta-analyses for RCTs and observational studies will be performed. For observational studies, the meta-analysis will be based on adjusted ORs if possible, and on crude ORs when adjusted ORs are not reported.

The main analysis will be a meta-analysis of the association between paracetamol exposure and genital tract malformations with a stratified analysis for boys and girls separately.

Separate meta-analyses for each secondary outcome, will be done for hypospadias, cryptorchidism, penile hypoplasia, enlargement of clitoris, fusion of labia, congenital malformations of vulva, congenital recto-vaginal fistula and anogenital distance.

Stratified analyses will be done according to the type of unexposed group (no treatment, other medications) will be performed.

Subgroup analysis will be performed according to the time of exposure during pregnancy.

Fixed and random-effects models will be used, and their results will be compared.

Statistical heterogeneity between studies will be evaluated by visually examining forest-plots and by using the Cochran's Q-test and I². An I² value > 50% or a p-value < 0.1 will be used to conclude to a substantial heterogeneity.

A sensitivity analysis will be performed to assess our results' robustness using only adjusted ORs.
The certainty of evidence will be assessed with the GRADE approach and GRADEpro software.

Analysis will be performed using R software version 4.2.235.

## Analysis of subgroups or subsets

A subgroup analysis according to relevant study level covariates (SLC) (study type (cohort, case-control), and the type of study prospective or retrospective is planned.

A subgroup analysis will be performed according to the risk of bias.

## Contact details for further information

Lina Eletri

Crat.secretariat.trs@aphp.fr

## Organisational affiliation of the review

Centre de référence sur les agents tératogènes (CRAT), Hôpital Trousseau, AP-HP. Sorbonne Université, Paris, France.

Pharmaco-épidémiologie et évaluation des soins (PEPITES), Institut Pierre Louis d'Epidémiologie et de Santé publique (iPLESP), INSERM U1136, Paris, France.

https://lecrat.fr

## Review team members and their organisational affiliations

Dr Lina Eletri. Department of Neonatology, Centre Hospitalier du Mans, 72037 Le Mans, France. Sorbonne Université, INSERM, Institut Pierre Louis d'Epidémiologie et de Santé Publique, AP-HP, Hôpital Trousseau, Département de Santé Publique, Centre de Référence sur les Agents Tératogènes (CRAT), F75012, Paris, France

Dr Kristen Joseph-Delaffon.

Professor Benoit Marin. Sorbonne Université, INSERM, Institut Pierre Louis d'Epidémiologie et de Santé Publique, AP-HP, Hôpital Trousseau, Département de Santé Publique, Centre de Référence sur les Agents Tératogènes (CRAT), F75012, Paris, France

Professor Delphine Mitanchez. Department of Neonatology, Bretonneau Hospital, François Rabelais University, F-37000 Tours, France, INSERM UMR_S 938 Centre de Recherche Saint Antoine, F-75012 Paris, France.

Professor Agnes Dechartres. Sorbonne Université, INSERM, Institut Pierre Louis d'Epidémiologie et de Santé Publique, AP-HP. Sorbonne Université, Hôpital Pitié Salpêtrière, Département de Santé Publique, Centre de Pharmacoépidémiologie (Cephepi), F75013, Paris, France

## Collaborators

Dr Jonathan Luke Richardson. Principal Medical Information Scientist and Data Manager. UK Teratology Information Service. Newcastle-upon-Tyne Hospitals NHS Foundation Trust and UK Health Security Agency

Professor Per Damkier. Department of Clinical Pharmacology. Head of Research Odense University Hospital, Department of Clinical Research University of Southern Denmark

Dr Elisabeth Elefant. AP-HP. Sorbonne Université, Hôpital Trousseau, Centre de référence sur les agents tératogènes, (CRAT), F75012, Paris, France

## Type and method of review

Epidemiologic, Meta-analysis, Systematic review
Anticipated or actual start date

17 April 2024

Anticipated completion date

01 July 2024

Funding sources/sponsors

The authors have not received a specific grant for this research.

Conflicts of interest

Language

English

Country

France

Stage of review

Review Ongoing

Subject index terms status

Subject indexing assigned by CRD

Subject index terms

MeSH headings have not been applied to this record

Date of registration in PROSPERO

26 April 2024

Date of first submission

15 April 2024

Stage of review at time of this submission
<table><thead><tr><td>Stage</td><td>Started</td><td>Completed</td></tr></thead><tbody><tr><td>Preliminary searches</td><td>Yes</td><td>No</td></tr><tr><td>Piloting of the study selection process</td><td>Yes</td><td>No</td></tr><tr><td>Formal screening of search results against eligibility criteria</td><td>No</td><td>No</td></tr><tr><td>Data extraction</td><td>No</td><td>No</td></tr><tr><td>Risk of bias (quality) assessment</td><td>No</td><td>No</td></tr><tr><td>Data analysis</td><td>No</td><td>No</td></tr></tbody></table>

The record owner confirms that the information they have supplied for this submission is accurate and complete and they understand that deliberate provision of inaccurate information or omission of data may be construed as scientific misconduct.

The record owner confirms that they will update the status of the review when it is completed and will add publication details in due course.

## Versions

26 April 2024

26 April 2024
<figure><img src="image_26.png" /></figure>

PRISMA 2020 Checklist

<table><thead><tr><th>Section and Topic</th><th>Item #</th><th>Checklist item</th><th>Location where item is reported</th></tr></thead><tbody><tr><td colspan="4"><strong>TITLE</strong></td></tr><tr><td>Title</td><td>1</td><td>Identify the report as a systematic review.</td><td>Manuscript, Title, page 1</td></tr><tr><td colspan="4"><strong>ABSTRACT</strong></td></tr><tr><td>Abstract</td><td>2</td><td>See the PRISMA 2020 for Abstracts checklist.</td><td></td></tr><tr><td colspan="4"><strong>INTRODUCTION</strong></td></tr><tr><td>Rationale</td><td>3</td><td>Describe the rationale for the review in the context of existing knowledge.</td><td>Manuscript, Introduction, page 7</td></tr><tr><td>Objectives</td><td>4</td><td>Provide an explicit statement of the objective(s) or question(s) the review addresses.</td><td>Manuscript, Introduction, page 9</td></tr><tr><td colspan="4"><strong>METHODS</strong></td></tr><tr><td>Eligibility criteria</td><td>5</td><td>Specify the inclusion and exclusion criteria for the review and how studies were grouped for the syntheses.</td><td>Manuscript, Methods, Eligibility criteria, pages 11</td></tr><tr><td>Information sources</td><td>6</td><td>Specify all databases, registers, websites, organisations, reference lists and other sources searched or consulted to identify studies. Specify the date when each source was last searched or consulted.</td><td>Manuscript, Methods, data sources and research strategy, page 12</td></tr><tr><td>Search strategy</td><td>7</td><td>Present the full search strategies for all databases, registers and websites, including any filters and limits used.</td><td>Manuscript, Methods, data sources and research strategy, page 12, Appendix 4</td></tr><tr><td>Selection process</td><td>8</td><td>Specify the methods used to decide whether a study met the inclusion criteria of the review, including how many reviewers screened each record and each report retrieved, whether they worked independently, and if applicable, details of automation tools used in the process.</td><td>Manuscript, Methods, study selection, page 12</td></tr><tr><td>Data collection process</td><td>9</td><td>Specify the methods used to collect data from reports, including how many reviewers collected data from each report, whether they worked independently, any processes for obtaining or confirming data from study investigators, and if applicable, details of automation tools used in the process.</td><td>Manuscript, Methods, data extraction process, page 13</td></tr><tr><td rowspan="2">Data items</td><td>10a</td><td>List and define all outcomes for which data were sought. Specify whether all results that were compatible with each outcome domain in each study were sought (e.g. for all measures, time points, analyses), and if not, the methods used to decide which results to collect.</td><td>Manuscript, Methods, outcomes, pages 11</td></tr><tr><td>10b</td><td>List and define all other variables for which data were sought (e.g. participant and intervention characteristics, funding sources). Describe any assumptions made about any missing or unclear information.</td><td>Manuscript, Methods, outcomes, pages 11</td></tr><tr><td>Study risk of bias assessment</td><td>11</td><td>Specify the methods used to assess risk of bias in the included studies, including details of the tool(s) used, how many reviewers assessed each study and whether they worked independently, and if applicable, details of automation tools used in the process.</td><td>Manuscript, Methods, risk of bias assessment, page 14</td></tr><tr><td>Effect measures</td><td>12</td><td>Specify for each outcome the effect measure(s) (e.g. risk ratio, mean difference) used in the synthesis or presentation of results.</td><td>Manuscript, Methods, Data synthesis, measures of association, page 14</td></tr><tr><td>Synthesis methods</td><td>13a</td><td>Describe the processes used to decide which studies were eligible for each synthesis (e.g. tabulating the study intervention characteristics and comparing against the planned groups for</td><td>Manuscript, Methods, Data synthesis, Meta-analysis, page 14</td></tr></tbody></table>
<figure><img src="image_27.png" /></figure>

PRISMA 2020 Checklist

<table><thead><tr><th>Section and Topic</th><th>Item #</th><th>Checklist item</th><th>Location where item is reported</th></tr></thead><tbody><tr><td></td><td></td><td>each synthesis (item #5)).</td><td></td></tr><tr><td></td><td>13b</td><td>Describe any methods required to prepare the data for presentation or synthesis, such as handling of missing summary statistics, or data conversions.</td><td>Not done</td></tr><tr><td></td><td>13c</td><td>Describe any methods used to tabulate or visually display results of individual studies and syntheses.</td><td>Manuscript, Methods, Data synthesis, Meta-analysis, page 15</td></tr><tr><td></td><td>13d</td><td>Describe any methods used to synthesize results and provide a rationale for the choice(s). If meta-analysis was performed, describe the model(s), method(s) to identify the presence and extent of statistical heterogeneity, and software package(s) used.</td><td>Manuscript, Methods, Data synthesis, Meta-analysis, page 15</td></tr><tr><td></td><td>13e</td><td>Describe any methods used to explore possible causes of heterogeneity among study results (e.g. subgroup analysis, meta-regression).</td><td>Manuscript, Methods, statistical analysis, meta-analysis, sensitivity and subgroup analysis, pages 15</td></tr><tr><td></td><td>13f</td><td>Describe any sensitivity analyses conducted to assess robustness of the synthesized results.</td><td>Manuscript, Methods, statistical analysis, meta-analysis, sensitivity analysis, pages 16</td></tr><tr><td>Reporting bias assessment</td><td>14</td><td>Describe any methods used to assess risk of bias due to missing results in a synthesis (arising from reporting biases).</td><td>Manuscript, Methods, statistical analysis, publication bias assessment, page 16</td></tr><tr><td>Certainty assessment</td><td>15</td><td>Describe any methods used to assess certainty (or confidence) in the body of evidence for an outcome.</td><td>Manuscript, Methods, statistical analysis, Certainty of evidence, page 16</td></tr><tr><td colspan="4"><strong>RESULTS</strong></td></tr><tr><td rowspan="2">Study selection</td><td>16a</td><td>Describe the results of the search and selection process, from the number of records identified in the search to the number of studies included in the review, ideally using a flow diagram.</td><td>Manuscript, Results, page 17, Figures, Figure 1</td></tr><tr><td>16b</td><td>Cite studies that might appear to meet the inclusion criteria, but which were excluded, and explain why they were excluded.</td><td>Manuscript, Results, page 17, Figures, Figure 1</td></tr><tr><td>Study characteristics</td><td>17</td><td>Cite each included study and present its characteristics.</td><td>Manuscript, Results, pages 17, Tables, Table 1</td></tr><tr><td>Risk of bias in studies</td><td>18</td><td>Present assessments of risk of bias for each included study.</td><td>Manuscript, Results, page 20, Figures, Figure 2</td></tr><tr><td>Results of individual studies</td><td>19</td><td>For all outcomes, present, for each study: (a) summary statistics for each group (where appropriate) and (b) an effect estimate and its precision (e.g. confidence/credible interval), ideally using structured tables or plots.</td><td>Supplementary tables, Table S1</td></tr><tr><td rowspan="4">Results of syntheses</td><td>20a</td><td>For each synthesis, briefly summarise the characteristics and risk of bias among contributing studies.</td><td>Manuscript, Results, page 20, Figures, Figure 2</td></tr><tr><td>20b</td><td>Present results of all statistical syntheses conducted. If meta-analysis was done, present for each the summary estimate and its precision (e.g. confidence/credible interval) and measures of statistical heterogeneity. If comparing groups, describe the direction of the effect.</td><td>Manuscript, Results, page 20, Figures, Figure 3 and 4</td></tr><tr><td>20c</td><td>Present results of all investigations of possible causes of heterogeneity among study results.</td><td>Manuscript, Results, page 21</td></tr><tr><td>20d</td><td>Present results of all sensitivity analyses conducted to assess the robustness of the</td><td>Manuscript, Results, pages 22, Supplementary figures, Figures S2,</td></tr></tbody></table>
<figure><img src="image_28.png" /></figure>

PRISMA 2020 Checklist

<table><thead><tr><th>Section and Topic</th><th>Item #</th><th>Checklist item</th><th>Location where item is reported</th></tr></thead><tbody><tr><td></td><td></td><td>synthesized results.</td><td>S3, S5, S6</td></tr><tr><td>Reporting biases</td><td>21</td><td>Present assessments of risk of bias due to missing results (arising from reporting biases) for each synthesis assessed.</td><td>Manuscript, Results, pages 20</td></tr><tr><td>Certainty of evidence</td><td>22</td><td>Present assessments of certainty (or confidence) in the body of evidence for each outcome assessed.</td><td>Manuscript, Results, pages 23, Tables, Table 2</td></tr><tr><td colspan="4"><strong>DISCUSSION</strong></td></tr><tr><td rowspan="4">Discussion</td><td>23a</td><td>Provide a general interpretation of the results in the context of other evidence.</td><td>Manuscript, Discussion, pages 25</td></tr><tr><td>23b</td><td>Discuss any limitations of the evidence included in the review.</td><td>Manuscript, Discussion, pages 30</td></tr><tr><td>23c</td><td>Discuss any limitations of the review processes used.</td><td>Manuscript, Discussion, pages 30</td></tr><tr><td>23d</td><td>Discuss implications of the results for practice, policy, and future research.</td><td>Manuscript, Discussion, pages 31</td></tr><tr><td colspan="4"><strong>OTHER INFORMATION</strong></td></tr><tr><td rowspan="3">Registration and protocol</td><td>24a</td><td>Provide registration information for the review, including register name and registration number, or state that the review was not registered.</td><td>Manuscript, Methods, page 10</td></tr><tr><td>24b</td><td>Indicate where the review protocol can be accessed, or state that a protocol was not prepared.</td><td>Manuscript, Methods, page 10</td></tr><tr><td>24c</td><td>Describe and explain any amendments to information provided at registration or in the protocol.</td><td>Not published, can be provided upon request</td></tr><tr><td>Support</td><td>25</td><td>Describe sources of financial or non-financial support for the review, and the role of the funders or sponsors in the review.</td><td>Manuscript, Funding, page 31</td></tr><tr><td>Competing interests</td><td>26</td><td>Declare any competing interests of review authors.</td><td>Manuscript, Conflict of interest, page 31</td></tr><tr><td>Availability of data, code and other materials</td><td>27</td><td>Report which of the following are publicly available and where they can be found: template data collection forms; data extracted from included studies; data used for all analyses; analytic code; any other materials used in the review.</td><td>Manuscript, Data availability, page 32</td></tr></tbody></table>

From: Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021;372:n71. doi: 10.1136/bmj.n71
# MOOSE (Meta-analyses Of Observational Studies in Epidemiology) Checklist

A reporting checklist for Authors, Editors, and Reviewers of Meta-analyses of Observational Studies. You must report the page number in your manuscript where you consider each of the items listed in this checklist. If you have not included this information, either revise your manuscript accordingly before submitting or note N/A.

<table><thead><tr><th>Reporting Criteria</th><th>Reported (Yes/No)</th><th>Reported on Page No.</th></tr></thead><tbody><tr><td><strong>Reporting of Background</strong></td><td></td><td></td></tr><tr><td>Problem definition</td><td>Yes</td><td>7</td></tr><tr><td>Hypothesis statement</td><td>Yes</td><td>7</td></tr><tr><td>Description of Study Outcome(s)</td><td>Yes</td><td>9</td></tr><tr><td>Type of exposure or intervention used</td><td>Yes</td><td>7</td></tr><tr><td>Type of study design used</td><td>Yes</td><td>7</td></tr><tr><td>Study population</td><td>Yes</td><td>11</td></tr><tr><td><strong>Reporting of Search Strategy</strong></td><td></td><td></td></tr><tr><td>Qualifications of searchers (eg, librarians and investigators)</td><td>Yes</td><td>10</td></tr><tr><td>Search strategy, including time period included in the synthesis and keywords</td><td>Yes</td><td>10</td></tr><tr><td>Effort to include all available studies, including contact with authors</td><td>Yes</td><td>14</td></tr><tr><td>Databases and registries searched</td><td>Yes</td><td>10</td></tr><tr><td>Search software used, name and version, including special features used (eg, explosion)</td><td>Yes</td><td>12</td></tr><tr><td>Use of hand searching (eg, reference lists of obtained articles)</td><td>Yes</td><td>11</td></tr><tr><td>List of citations located and those excluded, including justification</td><td>Yes</td><td>11</td></tr><tr><td>Method for addressing articles published in languages other than English</td><td>Yes</td><td>13</td></tr><tr><td>Method of handling abstracts and unpublished studies</td><td>Yes</td><td>13</td></tr><tr><td>Description of any contact with authors</td><td>Yes</td><td>14</td></tr><tr><td><strong>Reporting of Methods</strong></td><td></td><td></td></tr><tr><td>Description of relevance or appropriateness of studies assembled for assessing the hypothesis to be tested</td><td>Yes</td><td>11</td></tr><tr><td>Rationale for the selection and coding of data (eg, sound clinical principles or convenience)</td><td>Yes</td><td>12</td></tr><tr><td>Documentation of how data were classified and coded (eg, multiple raters, blinding, and interrater reliability)</td><td>Yes</td><td>13</td></tr><tr><td>Assessment of confounding (eg, comparability of cases and controls in studies where appropriate</td><td>Yes</td><td>14</td></tr></tbody></table>
<table><thead><tr><th>Reporting Criteria</th><th>Reported (Yes/No)</th><th>Reported on Page No.</th></tr></thead><tbody><tr><td>Assessment of study quality, including blinding of quality assessors; stratification or regression on possible predictors of study results</td><td>Yes</td><td>14</td></tr><tr><td>Assessment of heterogeneity</td><td>Yes</td><td>15</td></tr><tr><td>Description of statistical methods (eg, complete description of fixed or random effects models, justification of whether the chosen models account for predictors of study results, dose-response models, or cumulative meta-analysis) in sufficient detail to be replicated</td><td>Yes</td><td>15</td></tr><tr><td>Provision of appropriate tables and graphics</td><td>No</td><td></td></tr><tr><td><strong>Reporting of Results</strong></td><td></td><td></td></tr><tr><td>Table giving descriptive information for each study included</td><td>Yes</td><td>17</td></tr><tr><td>Results of sensitivity testing (eg, subgroup analysis)</td><td>Yes</td><td>22</td></tr><tr><td>Indication of statistical uncertainty of findings</td><td>Yes</td><td>23</td></tr><tr><td><strong>Reporting of Discussion</strong></td><td></td><td></td></tr><tr><td>Quantitative assessment of bias (eg, publication bias)</td><td>No</td><td></td></tr><tr><td>Justification for exclusion (eg, exclusion of non-English-language citations)</td><td>Yes</td><td>17</td></tr><tr><td>Assessment of quality of included studies</td><td>Yes</td><td>19</td></tr><tr><td><strong>Reporting of Conclusions</strong></td><td></td><td></td></tr><tr><td>Consideration of alternative explanations for observed results</td><td>Yes</td><td>29</td></tr><tr><td>Generalization of the conclusions (ie, appropriate for the data presented and within the domain of the literature review)</td><td>Yes</td><td>31</td></tr><tr><td>Guidelines for future research</td><td>Yes</td><td>31</td></tr><tr><td>Disclosure of funding source</td><td>Yes</td><td>31</td></tr></tbody></table>

Once you have completed this checklist, please save a copy and upload it as part of your submission. DO NOT include this checklist as part of the main manuscript document. It must be uploaded as a separate file.
# **Search queries**

## 1- PubMed search

Pregnancy and neonatal period:

#1 pregnancy[mh]

#2 pregnancy[tiab]

#3 pregnant women[mh]

#4 pregnancies [tiab]

#5 pregnant [tiab]

#6 gestation [tiab]

#7 infant,newborn[mh]

#8 newborn[tiab]

#9 neonate[tiab]

#10 offspring[tiab]

#11 prenatal[tiab]

#12 antenatal[tiab]

#13 perinatology[mh]

#14 perinatal[tiab]

#15 Prenatal Exposure Delayed Effects[mh]

#16 "in utero" [tiab]

#17 birth defect [mh]

#18 "birth defect" [tiab]

#19 "congenital abnormalities" [tiab]

#20 malformation [tiab]

#21 urogenital abnormalities [mh]

#22 "urogenital abnormalities"[tiab]

#23 cryptorchidism [tiab]

#24 cryptorchidism [mh]

#25 hypospadias [mh]

#26 hypospadias[tiab]
#27 "penile hypoplasia"[tiab]

#28 penis [mh]

#29 penis[tiab]

#30 "fusion of labia" [tiab]

#31 "labia adhesion" [tiab]

#32 "enlarged clitoris"[tiab]

#33 clitoris [mh]

#34 "rectovaginal fistula"[tiab]

#35 vulva[tiab]

#36 "anogenital distance"[tiab]

#37 #1 OR #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10 OR #11 OR
#12 OR #13 OR #14 OR #15 OR #16 OR #17 OR #18 OR #19 OR #20 OR #21 OR
#22 OR #23 OR #24 OR #25 OR #26 OR #27 OR #28 OR #29 OR #30 OR #31 OR
#32 OR #33 OR #34 OR #35 OR #36

Acetaminophen:

#38 paracetamol[tiab]

#39 paracetamol[mh]

#40 Acetaminophen [tiab]

#41 Acetaminophen [mh]

#42 APAP [tiab]

#43 p-Acetamidophenol [tiab]

#44 Acetamidophenol [tiab]

#45 N-Acetyl-p-aminophenol [tiab]

#46 Tylenol [tiab]

#47 Panadol [tiab]

#48 mild analgesics [tiab]

#49 #38 OR #39 OR #40 OR #41 OR #42 OR #43 OR #44 OR #45 OR #46 OR #47
OR #48
## 2- Embase search:

### Pregnancy and neonatal period:

#1 'pregnancy'/exp

#2 'pregnancy':ab,ti

#3 'pregnant woman'/exp

#4 'pregnant woman':ab,ti

#5 'pregnant':ab,ti

#6 'prenatal exposure'/exp

#7 'prenatal exposure':ab,ti

#8 'prenatal':ab,ti

#9 'antenatal':ab,ti

#10 'newborn'/exp

#11 'newborn':ab,ti

#12 'neonate':ab,ti

#13 'neonatology'/exp

#14 'neonatology':ab,ti

#15 'progeny'/exp

#16 'progeny':ab,ti

#17 'offspring':ab,ti

#18 'perinatal care'/exp

#19 'perinatal care':ab,ti

#20 'perinatal period'/exp

#21 'perinatal period':ab,ti

#22 'in utero':ab,ti

#23 'congenital malformation'/exp

#24 'congenital malformation':ab,ti
#25 'genital malformation'/exp

#26 'genital malformation':ab,ti

#27 'cryptorchidism'/exp

#28 'cryptorchidism':ab,ti

#29 'hypospadias'/exp

#30 'hypospadias':ab,ti

#31 'penis'/exp

#32 'penis':ab,ti

#33 'clitoris hypertrophy'/exp

#34 'clitoris hypertrophy':ab,ti

#35 'rectovaginal fistula'/exp

#36 'rectovaginal fistula':ab,ti

#37 'vulva'/exp

#38 'vulva':ab,ti

#39 'anogenital distance'/exp

#40 'anogenital distance':ab,ti

#41 #1 OR #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10 OR #11 OR
#12 OR #13 OR #14 OR #15 OR #16 OR #17 OR #18 OR #19 OR #20 OR #21 OR
#22 OR #23 OR #24 OR #25 OR

#26 OR #27 OR #28 OR #29 OR #30 OR #31 OR #32 OR #33 OR #34 OR #35 OR
#36 OR #37 OR #38 OR #39 OR #40

#42 'paracetamol'/exp

#43 'paracetamol':ab,ti

#44 'acetaminophen':ab,ti

#45 'APAP':ab,ti

#46 'p-Acetamidophenol':ab,ti

#47 'Acetamidophenol':ab,ti

#48 'N-Acetyl-p-aminophenol':ab,ti

#49 'Tylenol':ab,ti
#50 'Panadol':ab,ti

#51 'mild analgesics':ab,ti

#52 #42 OR #43 OR #44 OR #45 OR #46 OR #47 OR #48 OR #49 OR #50 OR #51

#53 #41 AND #52

### 3- Cochrane search:

#1 (pregnancy):ti,ab,kw

#2 MeSH descriptor: [Pregnancy] explode all trees

#3 (pregnant):ti,ab,kw

#4 ("pregnant women") :ti,ab,kw

#5 (gestation):ti,ab,kw

#6 MeSH descriptor: [Prenatal Exposure Delayed Effects] explode all trees

#7 (prenatal):ti,ab,kw

#8 (antenatal):ti,ab,kw

#9 MeSH descriptor: [Infant, Newborn] explode all trees

#10 (newborn):ti,ab,kw

#11 (neonate):ti,ab,kw

#12 (neonatology):ti,ab,kw

#13 (offspring):ti,ab,kw

#14 MeSH descriptor: [perinatology] explode all trees

#15 (perinatal):ti,ab,kw

#16 ("in utero") :ti,ab,kw

#17 MeSH descriptor: [urogenital abnormalities] explode all trees

#18 (urogenital abnormalities):ti,ab,kw

#19 MeSH descriptor: [congenital abnormalities] explode all trees

#20 (congenital abnormalities) : ti,ab,kw

#21 MeSH descriptor: [cryptorchidism] explode all trees

#22 (cryptorchidism):ti,ab,kw
#23 MeSH descriptor: [hypospadias] explode all trees

#24 (hypospadias):ti,ab,kw

#25 MeSH descriptor: [penis] explode all trees

#26 (penis):ti,ab,kw

#27 MeSH descriptor: [clitoris] explode all trees

#28 (clitoris):ti,ab,kw

#29 (labia):ti,ab,kw

#30 MeSH descriptor: [rectovaginal fistula] explode all trees

#31 (rectovaginal fistula):ti,ab,kw

#32 (anogenital distance):ti,ab,kw

#33 MeSH descriptor: [vulva] explode all trees

#34 (vulva): ti,ab,kw

#35 {OR #1-#34}

#36 MeSH descriptor: [Acetaminophen] explode all trees

#37 (acetaminophen):ti,ab,kw

#38 (paracetamol):ti,ab,kw

#39 (p-Acetamidophenol):ti,ab,kw

#40 (Acetamidophenol):ti,ab,kw

#41 (APAP):ti,ab,kw

#42 (N-Acetyl-p-aminophenol):ti,ab,kw

#43 (Tylenol):ti,ab,kw

#44 (panadol):ti,ab,kw

#45 ("mild analgesics"):ti,ab,kw

#46 {OR #36-#45}

#47 {AND #35,#46}

4- ICTRP basic search algorithm:
(pregnancy OR pregnant OR gestation OR pregnant women OR prenatal OR antenatal OR newborn OR neonate OR neonatology OR offspring OR perinatal OR perinatology) AND (paracetamol OR acetaminophen OR APAP OR p-Acetamidophenol OR Acetamidophenol OR N-Acetyl-p-aminophenol OR Tylenol OR Panadol) AND (birth defect OR congenital malformations OR urogenital tract malformation OR cryptorchidism OR hypospadias OR penile hypoplasia OR clitoris hypertrophy OR labia adhesion OR rectovaginal fistula OR vulva malformation OR anogenital distance)

5- [ClinicalTrials.gov search algorithm](#):

(paracetamol OR acetaminophen OR APAP OR p-Acetamidophenol OR Acetamidophenol OR N-Acetyl-p-aminophenol OR Tylenol OR Panadol) | (pregnancy OR pregnant OR gestation OR pregnant women OR prenatal OR antenatal OR newborn OR neonate OR neonatology OR offspring OR perinatal OR perinatology) | (birth defect OR congenital malformations OR urogenital tract malformation OR cryptorchidism OR hypospadias OR penile hypoplasia OR clitoris hypertrophy OR labia adhesion OR rectovaginal fistula OR vulva malformation OR anogenital distance)

**Data collection :**

The following data were collected for each of the included studies:

- General characteristics: first author name, publication year and journal, study period, country, language, and funding source.

- Study design, sample selection, source of data, and sample size.

- Population characteristics in both exposed and unexposed groups:

Maternal characteristics: maternal age, body mass index (BMI), parity, obstetrical history, maternal medical history (diabetes, hypertension, inflammation or fever during pregnancy), personal or family history of genetic disorders or congenital birth defects, use of co-medications (other medications), smoking and alcohol exposure.

Pregnancy outcomes: live birth, stillbirth, miscarriage, elective termination of pregnancy, birth weight.

Exposure: acetaminophen use, reason of prescription, dose during pregnancy, treatment duration and term of exposure, method of exposure measurement (questionnaire of use, pharmacy dispensing, prescription).
Control: the absence of treatment, or use of other medications (reason of prescription, dose, term of exposure), method of exposure measurement in case of exposure to other medications.

Outcomes: average gestational age at delivery (or other categorical variables relating to length of gestation such as preterm delivery [<37 weeks]), presence of cryptorchidism, age at diagnosis of cryptorchidism, age of orchiopexy, presence of hypospadias, anogenital distance, penile hypoplasia, enlargement of clitoris, fusion of labia, congenital malformations of vulva, congenital recto-vaginal fistula, method of outcome measurement, timing of outcome measurement, presence of other congenital malformations.

Study results: We collected, for both groups, the number of participants, the number of events for each outcome in each group, crude and adjusted measures of association between exposure and outcomes (OR, relative risk (RR) or hazard ratio (HR)) as well as 95% CI. Regarding the primary outcome measure, the composite criterion was planned to be either collected from original papers or reconstructed after data extraction and collection, following, if needed, contact with the authors.

For continuous variables, mean difference (MD) and standard deviation (SD) were collected.

Details regarding adjustment for relevant confounding factors regarding genital malformations (maternal age, gestational age, small for gestational age, pregestational diabetes, BMI, use of co-medications, socioeconomic status, family history of congenital malformations, smoking, alcohol use, and exposure to endocrine disruptor substances) were collected, as well as any other confounding factors considered in the original papers.
Appendix 5: List of meetings which were queried for eligible abstracts from the past 5 years.

- Organization of Teratology Information Specialists (OTIS) annual meeting

- European Teratology Society (ETS) annual meeting

- European Network of Teratology Information Services (ENTIS) annual meeting

- Teratology Society (TS) annual meeting

- International society of pharmacoepidemiology (ISPE) annual meeting

- International society of pharmacovigilance (ISOP) annual meeting

- Neonatology European Societies (jENS) biannual meeting

- American College of Obstetricians and Gynecologists (ACOG) annual clinical and scientific meeting.

- American Academy of Pediatrics (AAP) annual meeting

- Pediatric Endocrine Society (PES) annual meeting

- European Society for Pediatric Endocrinology (ESPE) annual meeting