Prenatal phthalate exposure and adverse birth outcomes in the USA: a prospective analysis of births and estimates of attributable burden and costs.

Background: Phthalates are synthetic chemicals widely used in consumer products and have been identified to contribute to preterm birth. Existing studies have methodological limitations and potential effects of di-2-ethylhexyl phthalate (DEHP) replacements are poorly characterised. Attributable fractions and costs have not been quantified, limiting the ability to weigh trade-offs involved in ongoing use. We aimed to leverage a large, diverse US cohort to study associations of phthalate metabolites with birthweight and gestational age, and estimate attributable adverse birth outcomes and associated costs.
Methods: In this prospective analysis we used extant data in the US National Institutes of Health Environmental influences on Child Health Outcomes (ECHO) Program from 1998 to 2022 to study associations of 20 phthalate metabolites with gestational age at birth, birthweight, birth length, and birthweight for gestational age z-scores. We also estimated attributable adverse birth outcomes and associated costs. Mother-child dyads were included in the study if there were one or more urinary phthalate measurements during the index pregnancy; data on child's gestational age and birthweight; and singleton delivery.
Findings: We identified 5006 mother-child dyads from 13 cohorts in the ECHO Program. Phthalic acid, diisodecyl phthalate (DiDP), di-n-octyl phthalate (DnOP), and diisononyl phthalate (DiNP) were most strongly associated with gestational age, birth length, and birthweight, especially compared with DEHP or other metabolite groupings. Although DEHP was associated with preterm birth (odds ratio 1·45 [95% CI 1·05-2·01]), the risks per log ₁₀ increase were higher for phthalic acid (2·71 [1·91-3·83]), DiNP (2·25 [1·67-3·00]), DiDP (1·69 [1·25-2·28]), and DnOP (2·90 [1·96-4·23]). We estimated 56 595 (sensitivity analyses 24 003-120 116) phthalate-attributable preterm birth cases in 2018 with associated costs of US$3·84 billion (sensitivity analysis 1·63- 8·14 billion).
Interpretation: In a large, diverse sample of US births, exposure to DEHP, DiDP, DiNP, and DnOP were associated with decreased gestational age and increased risk of preterm birth, suggesting substantial opportunities for prevention. This finding suggests the adverse consequences of substitution of DEHP with chemically similar phthalates and need to regulate chemicals with similar properties as a class.
Funding: National Institutes of Health.
Competing Interests: Declaration of interests LT acknowledges honoraria from Houghton Mifflin Harcourt, Audible, Paidos, and Kobunsha; travel support from the Endocrine Society, WHO, United Nations Environment Programme, Japan Environment and Health Ministries, and the American Academy of Pediatrics; and scientific advisory board activities for Beautycounter, IS-Global, and Footprint. MER acknowledges funding from the National Institute of General Medical Sciences, the National Institute of Environmental Health Sciences (NIEHS), and the New Hampshire Department of Environmental Services, as well as honoraria from the National Institutes of Health and UMass-Amherst, and advisory board relationships to the New England Graduate Women in Science and Engineering and Mill Run III Condo. AA acknowledges grant support from NIEHS. CN acknowledges the National Institute of Neurological Disorders and Stroke support. ESB acknowledges honoraria from the University of Rochester and SUNY-Downstate. All the authors have received funding from the NIH ECHO programme.
(Copyright © 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)