Phthalate exposure increases risk for preterm birth

A higher concentration of urinary phthalate metabolites in pregnant women is associated with a higher risk for preterm birth, according to a study published in JAMA Pediatrics.

“Having a preterm birth can be dangerous for both baby and mom, so it is important to identify risk factors that could prevent it," Kelly Ferguson, PhD, an epidemiologist at the NIH’s National Institute of Environmental Health Sciences (NIEHS), said in a press release.

A study conducted by Ferguson and colleagues in 2013 also found a significant association between phthalate exposure during pregnancy and preterm birth.

In the new study, Ferguson and colleagues obtained data from 16 U.S. studies that contained individual participant data on prenatal urinary phthalate metabolites and delivery timing to determine if there was an association between phthalate metabolites and the odds of preterm birth.

They evaluated exposures to 11 metabolites — monoethyl phthalate, mono-N-butyl phthalate, monoisobutyl phthalate, monobenzyl phthalate, mono (2-ethylhexyl) phthalate, mono (2-ethyl-5-hydroxyhexyl) phthalate, mono (2-ethyl-5-carboxypentyl) phthalate, mono (2-ethyl-5-oxohexyl) phthalate, mono (3-carboxypropyl) phthalate (MCPP), monocarboxy-isooctyl phthalate, and monocarboxy-isononyl phthalate — and adjusted the results for several variables, such as maternal age, race and ethnicity, education and prepregnancy body mass index.

The studies included 6,045 pregnant women who delivered between 1983 and 2018 and provided urine samples while they were pregnant. Among the women, 539 (9%) had a preterm birth.

Almost all urine samples — more than 96% — contained concentrations of most phthalate metabolites, except for mono (2-ethylhexyl) phthalate (83%) and MCPP (90%).

The odds of preterm birth were 12% to 16% higher with increased concentrations of four of the phthalate metabolites: Mono-N-butyl phthalate (OR = 1.12; 95% CI, 0.98-1.27), mono-isobutyl phthalate (OR = 1.16; 95% CI, 1-1.34), mono (2-ethyl-5-carboxypentyl) phthalate (OR = 1.16, 95% CI, 1-1.34), and mono (3-carboxypropyl) phthalate (OR = 1.14; 95% CI, 1.01-1.29). The other phthalate metabolites studied showed positive but nonsignificant associations.

Ferguson and colleagues estimated that hypothetical interventions to reduce the mixture of phthalate metabolite levels by 10% to 50% could prevent 1.8 to 11.1 preterm births per 1,000 live births.

Women can be exposed to phthalates through personal care products like cosmetics, their diet, household dust, food packaging, solvents, and detergents.

Ferguson and colleagues said reduced exposure to phthalates to protect pregnant women could be accomplished through interventions targeting consumer behaviors, companies taking actions to lower phthalates in their products, or changing standards and regulations.

“It is difficult for people to completely eliminate exposure to these chemicals in everyday life, but our results show that even small reductions within a large population could have positive impacts on both mothers and their children," Barrett Welch, PhD, a postdoctoral fellow at NIEHS, said in the press release.

Reference:

Preterm birth more likely with exposure to phthalates. https://www.nih.gov/news-events/news-releases/preterm-birth-more-likely-exposure-phthalates. Published July 11, 2022. Accessed July 12, 2022.