# Maternal-Foetal Effects of Exposure to Bisphenol A: Outcomes and Long-Term Consequences
## 5 Maternal-Foetal Effects of BPA
### Foetal Reproductive Function
Overall, in both studies, there was an association between maternal BPA concentrations and increased risk of preterm birth, either from BPA exposure alone [60] or from the mixture of BPA and di(2-ethylhexyl) phthalate (DEHP) [63]. Other studies that were performed during pregnancy found a sex-specific association. Specifically, [PERSON] et al. and [PERSON] et al. found that BPA exposure during pregnancy is associated with prematurity, but only in males [64; 65]. In the first study, one urine sample was collected from each of the 72 women in early pregnancy, from which higher levels of BPA were found to be related to a 1.1-day decrease in gestational age in males [64]. Similar results were found when analysing maternal serum from 2023 Chinese pregnant women, in which BPA alone and in mixture with other phenols were related to pre-term birth, with a higher susceptibility for male infants [65]. On the other hand, in the USA, two different studies also found an association, but only in pregnancies with girls. In 2015, [PERSON] et al. published an article where unconjugated BPA and BPA glucuronide were quantified in maternal plasma, acquired in the first trimester and at term, and in umbilical cord plasma. The results demonstrated a sex-specific relationship between increased levels of BPA at the end of gestation and increased gestational length of 1.1 days in pregnancies of female footuses [66]. Gathering 386 pregnant women from a fertility clinic, [PERSON] and co-workers compared urinary BPA levels from pre-term and non-pre-term pregnancies. Urinary samples were collected throughout gestation in all trimesters, and overall, BPA levels were significantly higher in the cases of pre-term birth, with an association between middle-late pregnancy levels and pre-term birth in female footuses only [67]. Despite being contradictory, these studies show a sex-specific effect of maternal BPA exposure that may be influenced by genetic susceptibility, sex hormones and the environment. However, when [PERSON] et al., [PERSON] et al. and [PERSON] et al. analysed BPA exposure and pre-term birth, there was no significant association [68; 69; 70]. These studies were all different, either in methodology or timeframe of BPA exposure. [PERSON] and colleagues analysed BPA levels in the urine of 130 pre-term and 352 full-term pregnant women (in all three trimesters) and found no significant differences between cases and controls. However, when the authors divided pre-term birth as spontaneous or of placental origin (due to PE or foetal growth restriction), there was an increase in spontaneous pre-term birth in late pregnancy, although few samples were provided at the fourth visit. Additionally, the stratification by sex also found an association between prematurity and BPA exposure, but only in females [68]. Despite the low evidence of general pre-term birth caused by gestational BPA exposure, these results seem to be in agreement with those previously described that found a sex-specific association. However, more studies are needed to confirm this hypothesis. When analysing BPA levels in pre- and post-implantation of the embryo in naturally conceiving pregnancies, no association was found with pre-term birth. Considering the episodic exposure and the short half-life of BPA, in this study, three urine samples from each participant were collected for 3 weeks for both groups (pre- and post-implantation) and then pooled in one sample to limit the variability of a single measurement [69]. From a different perspective, a Norwegian study analysed the adverse effects of polymer-based dental fillings during pregnancy. These polymers are extensively used for dental restorative treatment, and it has been shown that after the first hours of curing, endocrine disruptors, such as BPA, are released from these materials. Thus, the authors compared information regarding white filling placement during pregnancy with adverse birth outcomes and concluded that there were no significant associations [70].