Prenatal exposure to common environmental chemicals may be linked to postpartum depression (PPD) symptoms, according to a prospective cohort study.

In over 2,100 pregnant individuals, high-molecular-weight phthalates were associated with increased odds of PPD using both sensitive (Edinburgh Postnatal Depression Scale [EPDS] scores ≥10 and Center for Epidemiologic Studies Depression Scale [CES-D] scores ≥16) and specific (EPDS scores ≥13 and CES-D scores ≥20) definitions, reported Melanie H. Jacobson, PhD, MPH, of the NYU Grossman School of Medicine in New York City, and co-authors:

• Sensitive PPD definition: OR 1.11, 95% CI 1.00-1.23
• Specific PPD definition: OR 1.10, 95% CI 0.96-1.27

In addition, a 1-unit increase in log-transformed low-molecular-weight phthalates was associated with a 0.26-unit increase in Patient-Reported Measurement Information System (PROMIS) Depression scale T-score (95% CI -0.01 to 0.53, P=0.06), which corresponded to an OR of 1.08 (95% CI 0.98-1.19) when modeling PPD as a dichotomous outcome and using the sensitive PPD definition, they noted in JAMA Psychiatry.

However, results from linear regression analyses of continuous PROMIS depression T scores showed no statistically significant associations with any chemical exposures.

“This work underscores the importance of considering pregnancy a critical window of exposure to exogenous agents for maternal health outcomes after delivery, including psychiatric conditions,” the authors concluded.

Nearly all participants (>99%) had detectable levels of numerous phthalate metabolites and parabens.

These chemicals are used in the manufacturing of plastics, such as polycarbonate plastic products and plastic food wrap, and personal care products, such as lotions, cosmetics, soaps, and fragrances, and they are very common in our environment, Jacobson told MedPage Today in an email. “We are exposed to them everyday.”

PPD affects up to 20% of women after delivery, and can interfere with daily functioning, quality of life, and long-term health, the authors noted. PPD is also associated with poor mother-infant attachment, which can affect the child’s health and development.

“There are very few known Modifiable Risk Factors for PPD,” Jacobson said. “From a public health perspective, any avenues for PPD prevention would be important. Therefore, if these results are replicated, reducing exposure to these types of environmental chemicals may provide such an opportunity.”

While the underlying pathophysiology of PPD is still unclear, Jacobson suggested that these chemicals could be interfering with hormones during pregnancy, which would then increase vulnerability to PPD.

She and her team noted that “because of the temporal association between the dramatic changes in hormone concentrations at delivery and the onset of depressive symptoms in the postpartum period, the withdrawal of estrogen and progesterone after delivery is hypothesized to act as a biological trigger for some forms of PPD.”

“Thus, exogenous factors that affect hormones such as exposures to endocrine-disrupting chemicals (EDCs) are plausible contributors to PPD; however, they have not been sufficiently examined,” they wrote. “Given that potentially modifiable risk factors for PPD remain elusive, prenatal exposure to EDCs represents a novel interventional target.”

This prospective cohort study was conducted from 2006 to 2020 at five sites across the U.S., and included pooled data from five U.S. birth cohorts from the NIH Environmental Influences on Child Health Outcomes consortium.

The study participants were included if they had at least one test for urinary chemical concentrations of phenols, phthalate metabolites, parabens, or triclocarban during pregnancy, and had a self-reported postnatal depression screening assessment collected between 2 weeks and 1 year after delivery.

Of the 2,174 participants in the analysis, 49.8% were ages 26-34, 32.6% were white, 31.9% were Black, and 29.8% were Hispanic.

PPD was assessed a mean of 3 months after delivery. In total, 349 individuals (16.1%) screened positive for PPD using the sensitive definition, and 170 individuals (7.8%) screened positive using the specific definition.

Jacobson and team noted that additional sensitivity analyses using different strategies for modeling time-varying exposures and accounting for heterogeneity of effects by infant sex and timing of PPD assessment suggested that that results were robust.