Philips EM, et al. - Considering the increasing evidence suggesting the influence of exposure to synthetic chemicals, such as bisphenols and phthalates, on fecundability, researchers delineated the associations of first-trimester urinary concentrations of bisphenol A (BPA), BPA analogs, and phthalate metabolites with time to pregnancy (TTP). Findings revealed no links between bisphenols and phthalates with fecundability. Effects of bisphenols and phthalates on fecundability seemed to be influenced by preconception folic acid supplementation. Women exposed to these chemicals could be protected against reduced fecundability by administering folic acid supplements.

Methods

• First trimester urinary concentrations of bisphenols and phthalates were measured among 877 participants in the population-based Generation R pregnancy cohort (median gestational age, 12.9 weeks [interquartile range, 12.1, 14.4]).
• Associations of bisphenol and phthalate concentrations with TTP were examined using fitted covariate-adjusted Cox proportional hazard models.
• Researchers censored participants who conceived using infertility treatment at 12 months.
• They tested biologically plausible effect measure modification by folic acid supplement use.

Results

• No associations between bisphenol and phthalate compounds with fecundability were identified in the main models.
• Among women who did not use folic acid supplements preconceptionally, total bisphenols and phthalic acid were associated with longer TTP in stratified models, (respective fecundability ratios per each natural log increase were 0.90 [95% CI, 0.81 to 1.00] and 0.88 [95% CI, 0.79 to 0.99]).
• Researchers noted additional effect measure modification by folic acid supplement use for high-molecular-weight phthalate metabolites by using an interaction term for the exposure and folic acid supplement use.