Amniotic fluid absorption and growth functions in humans: what can we indirectly learn from congenital digestive atresias?
Authors: Parente Giovanni , Thomas Eduje , D’Antonio Simone , Pierangeli Francesco , Cordola Chiara , Libri Michele , Gargano Tommaso , Lima Mario 
Published: August 2022

Abstract
Background
Amniotic fluid (AF) was thought of just as a mechanical cushioning to the foetus. Nowadays, its role during pregnancy is getting more attention, suggesting hitherto unknown aspects. The aim of the study is to speculate on AF nutritional functions and its clinical repercussions based on what digestive tract (DT) atresias seem to suggest.

Methods
A retrospective analysis of the patients admitted to our department for DT atresias between 2000 and 2020 was conducted. Patients’ birth weight (BW), gestational age (GA) at birth and diagnosis were recorded. The following were excluded from the study: oesophageal atresias (OA) with tracheoesophageal fistula (TOF), colonic and anal atresias and patients with associated major comorbidities. A control group was made of patients admitted to our ward in the same period for congenital pulmonary airway malformations (CPAM). To standardize the BW, it was coupled with birth GA calculating the newborn percentiles. The mean newborn percentiles of OAs, duodenal atresias (DAs), jejunal atresias (JAs), and ileal atresias (IAs) were independently compared with the control group using Student’s t-test. Lastly, the significance of the frequencies’ distribution of newborns born small for gestational age (SGA) between the DT atresias and the control group was evaluated with the χ2 test, and the OR were calculated. A p-value < 0.05 was considered statistically significant.

Results
A total of 231 patients were eligible for the study: 36 OAs without TOF, mean BW 2488.8 ± 491 g (range 1630–3750 g), mean GA 36.8 ± 2.1 weeks (31–40 weeks), mean newborn percentile 18 ± 22 (1–75); 20 DAs, mean BW 2586.8 ± 577.9 g (1250–3462 g), mean GA 36.2 ± 2.5 weeks (31–40 weeks), mean newborn percentile 31 ± 23 (3–79); 17 JAs, mean BW 2483.5 ± 621.7 g (900–3205 g), mean GA 34.8 ± 2.1 weeks (30–38 weeks), mean newborn percentile 44 ± 28 (4–96); 17 IAs, mean BW 2646.1 ± 769.8 g (1162.0–3888 g), mean GA 35.9 ± 3.2 weeks (30–41 weeks), mean newborn percentile 44 ± 26 (1–82); and 141 CPAMs with mean BW 3287.4 ± 492.0 g (980–4580 g), mean GA 38.7 ± 1.8 weeks (26–41 weeks), mean newborn percentile 43 ± 26 (1–99). The number of SGA neonates was 18 between OA patients (50%), 4 between DAs (20%), 1 between JAs (6%), 2 between IAs (12%) and 11 between CPAMs (8%). The mean percentile of the OAs and DAs was lower than the control group with a p of < .01 and .03 while no statistical significance was found in the comparison between DAs, JAs, IAs and CPAMs with a p of .06, .86 and .59. The incidence of SGA in the control group resulted lower than the one in the DT atresias where it becomes higher the more proximal the atresia is (p < .05). The OR of SGA newborn in the OA group was 11.8, in DA 3.0, in JA 0.7 and in IA 1.6.

Conclusion
AF showed to have a great impact on foetal growth, and its preferred site of absorption seemed to be the stomach and duodenum. Its nutritional role could have an important predictive value in diagnosing DT atresia both prenatally and postnatally.