Perinatal Bisphenol Exposure and Small-for-Gestational-Age Neonates: The Evolving Effect of Replacements Then and Now.

Bisphenol analogues have been shown to have similar estrogenic activity to that of BPA and may affect fetal development. However, no human studies have examined the effects of perinatal exposure to emerging bisphenol alternatives [bisphenol G, bisphenol M, and bisphenol BP (BPBP)] on small for gestational age (SGA) and how placental function may mediate the relationship. Here, 13 urinary bisphenol analogues were detected in 1054 contemporary pregnant women, and BPA was still the most dominant congener. Logistic regressions identified BPA and its traditional alternatives [bisphenol B (BPB), bisphenol E (BPE), bisphenol Z, and bisphenol AP (BPAP)] as being associated with an elevated risk of SGA (all ORs > 1.80, P < 0.05). In contrast, the emerging substitutes, despite high occurrences, all showed much attenuated risk. Mixture effect models Bayesian kernel machine regression and quantile-based g-computation demonstrated that coexposure to bisphenols was strongly correlated with SGA risk (OR = 2.70, P < 0.001), with BPA and the conventional substitutes (BPB, BPE, and BPAP) as primary effect drivers, outweighing the effect from emerging substitutes. Finally, mediation analysis revealed that the placental function index estriol mediated the relationship between exposure and SGA, dominated by BPBP (25.4%). Our findings provide new epidemiological evidence that early BPA alternatives may pose a higher risk for offspring development than those emerging alternatives, potentially via mediation by compromised placental function. Future toxicity assessments and validation studies in other settings on these emerging bisphenols are needed.