2024-02-12 00:05:06
Research published in the journal The Lancet Planetary Health reveals that prenatal exposure to phthalate metabolites may increase the risk of preterm birth and low birth weight.
Study: Prenatal phthalate exposure and adverse birth outcomes in the US: a prospective analysis of births and estimates of attributable burden and costs. Image credit: Siberian Sun / Shutterstock
Background
Premature birth and low birth weight are associated with many negative consequences, including infant and girl mortality, psychological, behavioral and educational distress in young adulthood and cardiometabolic diseases in adulthood. In the United States, about 8% and 10% of babies had low birth weight and preterm birth, respectively, in 2020.
Many risk factors are associated with adverse birth outcomes, including maternal age, poor socioeconomic status, preeclampsia, and lack of prenatal care. Various synthetic chemicals, such as phthalates, are also known to increase the risk of birth distress.
Phthalate and its metabolites are used in personal care products and food packaging. These chemicals have pro-inflammatory, pro-oxidant and endocrine disrupting activities. The crossover between these pathways may disrupt the hormonal regulation during pregnancy and cause placental insufficiency, preeclampsia and early rupture of the membrane.
In this study, scientists investigated the effects of prenatal exposure to phthalates on birth weight and gestational age at birth. They also assessed adverse birth outcomes attributable to phthalates and associated costs.
study design
The scientists collected data from the National Institutes of Health’s Environmental Effects on Child Health Outcomes (ECHO), which includes 69 unique cohorts of children from across the US to identify environmental and preventable factors associated with low birth weight, preterm birth and other birth complications.
The concentrations of 20 phthalate metabolites were measured in maternal urine samples. The study analyzed the relationships of these metabolites with gestational age at birth, birth weight, birth length and birth weight for gestational age Z-scores (an age-independent assessment of fetal growth).
Important observations
The study was conducted on 5006 mother-child dyads identified from 13 groups in the ECHO program. The concentrations of phthalate metabolites in these mothers were similar to those detected in women of reproductive age in national surveys. A similar distribution of phthalates was observed across the tertiles. The metabolites of di-2-ethylhexyl phthalate (DEHP) showed a strong correlation with each other. Monoethyl phthalate and phthalic acid showed the highest concentrations in the maternal urine samples.
Higher concentrations of multiple phthalate metabolites were observed in non-Hispanic black mothers. In contrast, Hispanic mothers showed higher concentrations of low molecular weight metabolites and lower concentrations of high molecular weight metabolites, DEHP and phthalic acid.
An inverse relationship was observed between maternal age and the concentrations of all metabolites. Moreover, a positive relationship was observed between maternal age, birth weight and length.
Effect of phthalates on birth outcomes
The study analysis revealed strong associations of phthalic acid, diisodecyl phthalate (DiDP), di-n-octyl phthalate (DnOP) and dizononyl phthalate (DiNP) with gestational age, labor length and birth weight. These associations were stronger than that observed for low and high molecular weight metabolites and DEHP.
Overall, phthalate metabolites showed an association with low birth weight. The strongest associations were observed between concentrations of phthalic acid, DiNP, DiDP and DnOP and preterm birth and low birth weight. The strength of these associations was stronger in the third trimester compared to that in the first and second trimesters.
The findings of sensitivity analysis revealed that the association between DnOP and preterm birth is stronger for female infants than male infants. Moreover, the associations of phthalic acid, DiNP, and DnOP with many birth outcomes were stronger among non-Hispanic white mothers and college-educated mothers.
Regarding adverse birth outcomes attributable to phthalates and associated costs, the study estimated 56,595 preterm births in 2018, with associated costs of $3.84 billion. A sensitivity analysis examining DiDP exposure revealed 57,017 to 79,947 attributable cases with associated costs of $3.86 billion to $5.42 billion. Similarly, for DiNP exposure, the analysis showed 76,838 to 120,116 attributable cases with associated costs of $5.21 billion to $8.14 billion.
The meaning of the study
The study reveals that prenatal exposure to phthalate metabolites can increase the risk of preterm birth and low birth weight. The pattern of associations observed in the study suggests that phthalate metabolites that replace DHEP in food packaging are responsible for the increase in preterm birth. This indicates a need to regulate chemicals with similar properties as a class.
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