The association between maternal urinary phthalate concentrations and blood pressure in pregnancy: The HOME Study

BACKGROUND Exposure to phthalates, a class of endocrine disrupting chemicals, is ubiquitous. We examined the association of urinary phthalate metabolite concentrations during pregnancy with maternal blood pressure and risk of pregnancy-induced hypertensive diseases. METHODS We used data from the Health Outcomes and Measures of the Environment Study, a prospective birth cohort of low-risk pregnant women recruited between March 2003 and January 2006. We analyzed maternal urine samples collected at 16 and 26 weeks gestation for 9 phthalate monoester metabolites reflecting exposure to 6 phthalate diesters. Outcomes included maternal blood pressure at <20 and ≥ 20 weeks gestation and pregnancy induced hypertensive diseases (gestational hypertension, preeclampsia, eclampsia, and HELLP syndrome). RESULTS Data were available for 369 women who gave birth to singleton, live-born infants without congenital anomalies. Of the phthalate metabolites evaluated, only mono-benzyl phthalate (MBzP) concentrations were significantly associated with maternal diastolic blood pressure at <20 weeks gestation. Women in the third MBzP tercile at 16 weeks gestation had diastolic blood pressure 2.2 (95% CI: 0.5-3.9) mm Hg higher at <20 weeks gestation and 2.8 (95% CI: 0.9-4.7) mm Hg higher at ≥ 20 weeks gestation compared to women in the first tercile. Compared to women in the first tercile, women in the top MBzP tercile at 16 weeks had an increased risk of developing pregnancy-induced hypertensive diseases (RR = 2.92, 95 % CI 1.15-7.41, p-value for trend = 0.01). MBzP concentrations at 26 weeks gestation were not as strongly associated with blood pressure at ≥ 20 weeks gestation or risk of pregnancy-induced hypertensive diseases. CONCLUSION This study suggests that maternal urinary MBzP concentrations may be associated with increased diastolic blood pressure and risk of pregnancy-induced hypertensive diseases.