Prenatal Exposure to Phthalates and Maternal Metabolic Outcomes in a High-risk Pregnant Latina Population

Background: Phthalates are a group of endocrine disrupting chemicals that are heavily used throughout industry in flexible plastic and personal-care products. As a result, detectable levels of their metabolites are readily found in humans. Some studies have shown associations of phthalates with diabetes, but associations with gestational diabetes mellitus (GDM) are less clear.

Objective: To investigate the association of 11 prenatal urinary phthalate metabolites and development of GDM, impaired glucose tolerance (IGT), continuous plasma glucose level, and excessive gestational weight gain (GWG) in a population of pregnant Latina women (N = 415) enrolled in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) cohort study.

Methods: Phthalate metabolite levels were measured via mass spectrometry from two urine samples collected in the end of the first and second trimester. Maternal plasma glucose levels, prior diabetes diagnosis, GDM diagnosis, and weight gain were abstracted from medical records. Multiple regression was used to evaluate the association between the average of the two urinary phthalate metabolites levels and maternal metabolic outcomes. In our sensitivity analysis, phthalate levels were categorized by level (as quartiles of exposure) and by timing of urine sample collection (as taken in first and second half of pregnancy).

Results: Consistent with findings from a nationally representative sample, all of the individual phthalate metabolites were detected in majority of mothers. Thirty-one mothers (7.5%) were diagnosed with GDM, 49 mothers (14.7%) displayed IGT, and 223 mothers (55.1%) gained an excessive amount of weight during their pregnancy. MEP concentrations were associated with an increased odds of excessive GWG (OR: 1.1, 95% CI: 1.0 to 1.3). We did not find an association between any phthalate metabolite and any maternal glucose outcome.

Conclusion: Contrary to previous studies, our findings do not support an association of prenatal phthalate levels and increased odds for hyperglycemia, IGT, or GDM. But, we did find an increased odds of excessive GWG, a well-known risk factor for GDM.