Phthalate exposure and stressful life events in pregnancy have a joint effect on preterm birth

Abstract

TPS 632: Health effects of flame retardants and plasticizers, Johan Friso Foyer, Floor 1, August 27, 2019, 3:00 PM - 4:30 PM Background: Urinary phthalate metabolites and psychological stress in pregnancy have been individually associated with preterm birth (PTB), but no study has examined the joint effect of these two environmental exposures. We hypothesized that there would be stronger associations between phthalate exposure and PTB in mothers with higher stress in pregnancy compared to mothers with lower stress. Methods: We addressed this question using data from The Infant Development and the Environment Study (TIDES), a prospective birth cohort conducted at four US sites (N=785). Urinary phthalate metabolite concentrations were measured in samples collected in the first and third trimesters of pregnancy. Stressful life events (SLE) during gestation were assessed by a questionnaire administered in the third trimester. PTB was defined as delivery before 37 weeks completed gestation (n=71). We examined associations between urinary phthalate metabolite concentrations at each visit in association with PTB using logistic regression models adjusted for maternal race, age, pre-pregnancy body mass index, specific gravity, and gestational age at sample collection. Results: Summed di-2-ethylhexyl phthalate (ΣDEHP) metabolites measured in urine samples from the third trimester, but not the first trimester, were associated with an increased odds ratio (OR) of PTB (OR=1.38, 95% confidence interval [CI] =1.01, 1.89). In models stratified by SLE, associations between third trimester ΣDEHP concentrations and PTB were significant only for women experiencing 1 or more SLE during pregnancy (OR: 2.05, 95% CI: 1.28, 3.29) but not for women with no SLE during pregnancy (OR: 0.99, 95% CI: 0.63, 1.55); the interaction was marginally significant (p=0.05). Conclusions: We observed an association between urinary ΣDEHP levels and PTB that was modified by psychological stress in pregnancy. Additional research to understand the joint effects of chemical as well as non-chemical exposures is necessary in order to advance the state of the science on how the environment impacts pregnancy.