Associations between phenols and phthalates and placental weight in a mother-child cohort with improved exposure assessment

Background and Aim: The placenta plays a key role in assuring a normal foetal development and growth. Few epidemiological studies have investigated the effects of phenols and phthalates on placental function. We aimed to explore whether maternal exposure to phenols and phthalates during the second and third pregnancy trimesters are associated with changes in placental weight at birth and placental-to-birth weight ratio (PFR). Methods: We relied on a subsample of 357 women from the French SEPAGES cohort with placental and birth weights assessed, and for whom 8 phenols (4 parabens, 2 bisphenols, triclosan and benzophenone-3), 13 phthalate metabolites and 2 non-phthalate plasticizer metabolites were measured in within-subject pools of repeated urine samples collected at second and third pregnancy trimesters (median= 21 samples/trimester). Adjusted linear regressions were used to evaluate the associations between each compound and placental weight or PFR. Results: Each ln-unit increase in urinary monobenzyl phthalate (MBzP) concentrations at the second and third trimesters was associated with a mean placental weight decrease of 19.67 g (95%CI: -37.94; -1.4) and 16.71 g (95%CI: -33.08; -0.33), respectively. A decrease in PFR was also observed with MBzP exposure at the second (β: -0.51; 95%CI: -0.99; -0.04) and third trimester (β: -0.46; 95%CI: -0.88; -0.03). Children born to mothers with detected/quantified bisphenol S (BPS) in the second trimester showed a significantly lower PFR compared to mothers with undetected BPS (β: -0.83, 95%CI: -1.57; -0.09). No associations were observed with the remaining compounds. Conclusions: This is the first study exploring the effect of BPS maternal exposure on placental function in humans. Our MBzP results are consistent with a previous study that found a similar negative association on placental function in girls, whereas three other studies relying on spot urine samples reported null associations. Keywords: placental weight, phenols, phthalates, pfr, prenatal exposure