Environment/Climate Change
Prenatal exposure to phthalate mixtures and birthweight – Findings from an Ethnically Diverse U.S. Pregnancy Cohort (2010-2015). Shabnaz Siddiq* Shabnaz Siddiq Jeanette A. Stingone Andrew Rundle John Meeker Virginia Rauh Susannah Leisher Pam Factor-Litvak
Background: Prenatal exposure to phthalate metabolites (PthM) is widespread and may affect maternal-fetal health. This study investigates associations between a prenatal PthM mixture and birthweight in a diverse U.S. sample.
Methods: We analyzed 951 controls (without pregnancy complications) from a nested matched case control study embedded in the Nulliparous Mothers to Be Study who provided 1-3 urine samples (total n=2723) throughout pregnancy. Eleven PthM were measured. . Birthweight (in grams) was recorded at delivery. Bayesian Weighted Quantile Sum (BQWS) regression estimated associations between PthM mixtures and birthweight, with stratification by maternal BMI and race/ethnicity and infant sex.
Results: Mean infant birthweight was 3393.8g (SD=473.9g). Each quartile increase in PthM mixture was associated with lower infant birthweight (β = -72.9g, 95% CI -116.6, -28.5), with Mono-isobutyl phthalate (MiBP) (weight (w) = 0.18), Monoethyl phthalate (MEP) (w = 0.18), and Monobenzyl phthalate (MBzP) (w = 0.10) contributing most to the mixture’s effect. Among underweight/normal weight women, increase in the mixture was associated with a -85.3g (95% CI: -137.0, -35.9) decrease in infant birthweight. The decrease was -71.3g (95% CI: -128.6, -14.5) for women carrying female infants and -45.8g (95% CI: -101.2, 9.6) for women carrying male infants. Among infants born to Non-Hispanic White women, the decrease in birthweight was -71.8g (95% CI: -125.5, -19.6); -52.4g (95% CI: -110.7, 5.9); for infants born to Hispanic women; and -36.2g (95% CI: -90.8, 18.4) for infants born to Non-Hispanic Black women. MBZP and MiBP played prominent roles in the stratum-specific results.
Conclusions: The findings suggest that prenatal exposure to a PthM mixture decreased infant birthweight, with MiBP and MBZP playing important roles. Given the pervasiveness of phthalate exposure, even modest decreases in average infant birthweight could have significant population-level impacts.