Urinary phthalate metabolite concentrations and maternal weight during early pregnancy

Phthalates are a class of chemicals that may be associated with obesity in non-pregnant populations. Little is known about the association between pregnancy phthalate exposure and maternal obesity.

We evaluated the association between early-pregnancy urinary concentrations of specific phthalate metabolites and the distribution of body mass index (BMI, cross-sectional), and early gestational weight gain (GWG, prospective).

We measured 1st trimester urinary phthalate metabolite concentrations (median 9.9 weeks gestation) in 347 women from the LIFECODES pregnancy cohort (Boston, MA), who delivered term births. All measures were adjusted for specific-gravity and log-transformed. We used quantile regression to evaluate shifts in the entire outcome distributions, calculating multivariable-adjusted differences in the associations between these phthalate metabolites and BMI and GWG at the 25th, 50th, and 75th percentiles of these anthropometric outcomes.

Higher concentrations of mono-ethyl phthalate (MEP) were associated with a rightward shift of 2.8kg/m² at the 75th percentiles of BMI (lowest vs highest quartile, 95% CI: 0.2-5.4) and 1.3kg at the 75th percentiles of early GWG (lowest vs second quartiles, 95% CI: 0.3-2.4). A significant right-shift in the upper tail of BMI was also observed at higher concentrations of mono-benzyl (MBzP), mono-3-carboxypropyl (MCPP), and a summary measure of di-(2-ethylhexyl) phthalate metabolites (∑DEHP). ∑DEHP was also associated with lower GWG.

Certain phthalates may be associated with shifts in maternal obesity measures, with MEP, MBzP, MCPP, and ∑DEHP being cross-sectionally associated with 1st trimester BMI and MEP and ∑DEHP being positively and inversely associated with early GWG, respectively.