Urinary concentrations of phthalate metabolites during gestation and intrahepatic cholestasis of pregnancy: a population-based birth cohort study

Phthalates, a class of widely used endocrine-disrupting chemicals (EDCs), are toxic to various organ systems in animals and humans. Intrahepatic cholestasis of pregnancy (ICP) is a reversible liver dysfunction causing cholestasis in late pregnancy. Evidence on the associations between exposure to phthalates and ICP is still lacking. In the present study, we investigated the relationships between urinary concentrations of phthalate metabolites and the risk of ICP in a Chinese population-based birth cohort. Pregnant women participated in the Ma’anshan Birth Cohort (MABC) study in China. Seven phthalate metabolites were detected in a urine sample in early pregnancy. Chemical concentrations were grouped by quartiles, and associations with outcomes were examined using logistic regression with adjustment for urine creatinine, race, education, poverty status, smoking status, alcohol consumption, maternal age, prepregnancy body mass index (BMI), parity, twin pregnancy, and pregnancy-related liver complications. Of 3474 women recruited into the Ma’anshan Birth Cohort, 2760 met the inclusion criteria and contributed to further analysis and biomonitoring data. Elevated odds ratios (ORs) of ICP were observed in the highest quartiles of monomethyl phthalate (MMP) exposure (OR = 1.59, 95% confidence intervals (CI) = 1.01–2.51) and monobutyl phthalate (MBP) exposure (OR = 1.82, 95% CI = 1.16–2.85) in the adjusted analyses. Our findings add to the evidence that supports the role of maternal phthalate exposure in the first trimester of gestation as a risk factor for ICP.