Phenols, Parabens and Triclocarban During Pregnancy: Associations with Maternal Hormones and Birth Outcomes and the Modifying Effect of Maternal Stress

Abstract

Gestational age at delivery and birth weight are important predictors of fetal and infant health. Preterm infants and infants born with a low birth weight are at risk to a host of adverse health effects including neurological disabilities, breathing problems and chronic diseases later in life. Puerto Rico has one of the highest rates of preterm birth in the U.S. and the reasons behind this elevated rate are unclear. Chemical exposure during pregnancy could impact the mother, leading to adverse birth outcomes, or could pass through the placenta and directly impact the fetus. These adverse effects could potentially occur with very low concentrations of chemicals due to the vulnerable period of development. Phenols, parabens and triclocarban are a group of ubiquitous chemicals commonly found in personal care products and household items. These chemicals have been detected in the majority of the U.S. population, and a cohort in Puerto Rico, PROTECT, has higher concentrations of these chemicals as compared to the U.S. mainland. Phenols, parabens and triclocarban have also been linked to a number of growth parameters during pregnancy and at birth, including birth weight and gestational length. Endocrine disruption is a suspected pathway leading to these health outcomes. This dissertation focuses on the associations between urinary biomarkers of phenols, parabens and triclocarban on birth outcomes. The association between the exposure biomarkers and maternal hormones is also explored as a potential pathway. Maternal stress could modify the association between the exposure biomarkers and birth outcomes given the similar pathways involved between stress and gestational length. Therefore, the interaction between stress and the exposure biomarkers was explored. Aim 1 focused on the associations between the exposure biomarkers and maternal hormones in two study populations of pregnant women. The exposure biomarkers were associated with altered thyroid and reproductive hormones in the mother. Aim 2 and 3 were focused on the main dissertation cohort in Puerto Rico, PROTECT. Aim 2 found changes in gestational length with higher concentrations of some of the biomarkers of exposure. Benzophenone-3, bisphenol-A, methylparaben and propylparaben were associated with an increase in gestational length, with stronger associations observed at the 16-20 weeks gestation time point in comparison to 24-28 weeks. There was also evidence of a change in birth size with increased concentrations of the exposure biomarkers. Triclosan was associated with a higher odds of small for gestational age (SGA), and benzophenone-3 was associated with a higher odds of being large for gestational age (LGA). The relationship between bisphenol-S and birth size differed by study visit. At 16-20 weeks gestation, bisphenol-S was associated with LGA; however, at 24-28 weeks gestation, bisphenol-S was associated with SGA. Aim 3 examined the modifying effect of maternal stress on the association between the exposure biomarkers and gestational length. Associations between exposure biomarkers and gestational length were stronger in the presence of an overall negative score of the life event survey, indicating maternal stress due to negative life events may make pregnancies more vulnerable to chemical exposure. Overall, these results add to the growing literature on the effects of phenols, parabens and triclocarban on pregnancy. Further studies are required to confirm these findings, particularly the temporal differences observed. This is the first study to look into the modifying effect of maternal stress and these associations, and more studies are needed to confirm the findings observed.