Chemical exposure may increase risk of preterm birth, study finds

Exposure to phthalates during pregnancy may be a risk factor for preterm birth, according to a study recently published in JAMA Pediatrics.

Phthalates are a variety of common chemicals found in personal care products, such as cosmetics, as well as detergents, food packaging, and solvents.

Increased phthalate exposure was found to be associated with a 12%-16% greater chance of preterm birth, suggesting a need for public health and policy measures to reduce exposures in pregnant individuals.

“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, an epidemiologist at the National Institute of Environmental Health Sciences (NIEHS), said in a statement.

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To understand the prospective association between phthalate exposure and preterm birth, researchers conducted a systemic review of 16 prospective preconception and pregnancy studies in the United States.

The study is believed to be the largest prospective investigation of phthalate exposure in pregnancy and preterm birth to date with a diverse study population.

Participants included pregnant individuals who delivered between 1983 and 2018 and provided 1 or more urine samples during pregnancy.

Urinary phthalate metabolites were used as biomarkers of phthalate exposure in this study. Researchers used logistic regression models to examine the association between each phthalate metabolite with odds of preterm birth, adjusting for maternal age, race and ethnicity, education and pre-pregnancy body mass index. Preterm birth was defined as less than 37 weeks of gestation at delivery.

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Researchers also considered the potential influence of exposure to an overall phthalate mixture, evaluating how hypothetical interventions to reduce exposure could impact preterm birth.

The analytic sample included 6,045 participants with a mean age of 29.1 years, 9% of which delivered preterm. Of the total participants, 13.3% were Black, 38.4% were Hispanic or Latina, 42.6% were white and 5.4% had another race or ethnicity.

Phthalate metabolites were detected in more than 96% of participants. Overall, higher urinary metabolite concentrations for several phthalates were associated with greater odds of delivering preterm.

There were approximately 90 preterm births per 1,000 live births in this study population. Researchers estimated that hypothetical interventions could prevent 2 to 32 preterm births per 1,000 live births. Specifically, hypothetical interventions to reduce the mixture of phthalate metabolite levels by 10%, 30% and 50% were estimated to prevent 1.8, 5.9 and 11.1 preterm births, respectively.

These findings suggest that exposure to multiple phthalates is associated with an increased risk of preterm birth. However, the authors acknowledge that their analysis required assumption of causality, so their results must be interpreted with caution.

They assert that their findings provide evidence of the need to reduce phthalate exposures among pregnant individuals.

“Given that most individuals are exposed to multiple phthalates, regulatory approaches to mitigate population-level health effects from phthalates would be most effective when considering phthalates as a class, rather than as individual chemicals,” wrote the authors.

Behavioral interventions, including selecting phthalate-free care products and altering one’s diet, can reduce phthalate exposure. However, the number of products containing phthalates and the lack of FDA regulations can make it difficult to implement these behavioral changes, especially for certain populations affected by economic disparities.

The authors encourage federal and state regulations, as well as voluntary action from retailers and manufacturers to reduce phthalate exposure and protect pregnancy.

“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, Ph.D., a postdoctoral fellow at NIEHS said in a statement.

The researchers plan to conduct additional studies to better understand the mechanisms by which exposure to phthalates can affect pregnancy, with the intention of determining if there are effective ways for mothers to reduce their exposures.

Reference

Welch B M, Keil A P, Buckley J P, et al. Associations Between Prenatal Urinary Biomarkers of Phthalate Exposure and Preterm Birth: A Pooled Study of 16 US Cohorts. JAMA Pediatrics. 2022. https://jamanetwork.com/journals/jamapediatrics/article-abstract/2794076. Published July 11, 2022. Accessed July 19, 2022.