In a New York-based, prospective birth-cohort study published in the journal Environment International, researchers investigated the potential association between maternal urinary concentrations of bisphenols and phthalates during pregnancy and child adiposity outcomes from birth to four years. They found associations between prenatal exposure to bisphenols and high-molecular-weight (HMW) phthalates and childhood weight and body mass index (BMI) at ages three and four years.
Study: Fetal bisphenol and phthalate exposure and early childhood growth in a New York City birth cohort
Background
Growth patterns during infancy and early childhood are pivotal indicators of future health. Rapid weight gain in infancy is linked to childhood obesity and various health issues later in life. Exposure to endocrine-disrupting chemicals like bisphenols and phthalates during pregnancy can disrupt fetal development, impacting early-life growth. These chemicals, extensively used in consumer products, pose health risks due to their ability to cross the placental barrier and interfere with hormonal systems. These chemicals induce oxidative stress and inflammation, potentially affecting fetal development and subsequent growth.
However, research on the association between exposure to these chemicals during pregnancy and child growth has yielded conflicting results, possibly due to differences in study populations and measurement timing during pregnancy. Additionally, newer substitutes for well-studied chemicals like bisphenol A (BPA) and di-2-ethylhexyl phthalate (DEHP) have been understudied in this context. Therefore, researchers in the present study investigated the potential link between prenatal levels of bisphenols and phthalates in the urine of mothers and adiposity outcomes of their children from birth to four years of age.
About the study
This study included 1091 mother-child pairs from the New York University Children’s Health and Environment Study (NYU CHES), a cohort following participants from pregnancy into childhood, with urinary bisphenol and phthalate measurements during pregnancy and data on child adiposity up to four years of age. Mothers had a mean age of 31.8 years, with 52.6% of them Hispanic and 31.1% of them being Non-Hispanic White.
Maternal spot urine samples collected during early, mid, and late pregnancy were analyzed for bisphenols and phthalates. Phthalate metabolites were measured using high-performance liquid chromatography-electrospray ionization tandem mass spectrometry, while bisphenols were measured using the same method. Urinary creatinine was measured to account for dilution. Detected metabolites were grouped into low-molecular-weight (LMW), HMW phthalates, and total bisphenols (ΣBP). Creatinine-adjusted metabolite concentrations were calculated to correct for urinary dilution. Values below the limit of detection were imputed. Pregnancy-averaged exposures were calculated based on one to three measurements.
Further, weight, height, and skinfold thickness were used as indicators of child adiposity and growth, applying international growth standards. Birthweight and child sex were obtained from health records. Weight-for-height z-scores were determined from the INTERGROWTH-21 standard. Measurements were taken at ages 1, 2, and 3-5 years. Infant weight change categories were constructed based on standard deviation score (SDS) change from birth to one or two years. Growth acceleration was defined as >0.67 SDS weight increase, normal growth as <0.67 SDS increase/<0.67 SDS decrease, and growth deceleration as >0.67 SDS decrease between time points.
Maternal demographic and lifestyle information was collected via prenatal questionnaires, while maternal age, pre-pregnancy BMI, and parity were obtained from electronic medical records. Statistical methods included Spearman correlation analysis, linear mixed-effects models (LME) interaction analysis, sensitivity analysis, logistic regression, and adjustment for predefined confounders.
Results and discussion
The study found no significant associations between pregnancy-averaged bisphenol and phthalate concentrations and child adiposity outcomes after correcting for multiple testing. However, the second-trimester ΣBP and BPA were found to be associated with higher child weight between 0 and 4 years of age. Further, no trimester-specific associations were found for overall child BMI or skinfold thicknesses.
Associations were found between higher prenatal exposure to specific phthalate metabolites, such as mono-(2-carboxymethyl) phthalate (mCMHP), and child weight at three years. Associations were also found between child weight at four years and ΣHMW, ΣDEHP, mono-(2-ethyl-5-carboxypentyl) phthalate (mECPP), mCMHP, and mono-(2-ethylhexyl) phthalate (MEHP). Similarly, higher prenatal concentrations of ΣHMW, ΣDEHP, mECPP, mono-(2-ethylhexyl) 5-hydroxyhexyl phthalate (mEHHP), and mono-2(ethyl-5-oxohexyl) phthalate (mEOHP) were associated with increased child BMI at four years.
Sex-specific analysis showed non-significant associations between exposure and overall adiposity outcomes for boys and girls. Additionally, no significant associations were found between maternal pregnancy-averaged urinary concentrations of bisphenols or phthalates and infant growth deceleration or acceleration.
Conclusion
In conclusion, the study found positive associations between maternal second-trimester urinary ΣBP and BPA concentrations and child weight from birth to four years, as well as between pregnancy-averaged ΣHMW and HMW phthalate metabolites and child weight/BMI at ages three and four. These findings add to existing knowledge on prenatal bisphenol and phthalate exposure effects. Future research should include multi-cohort studies with diverse populations and repeated prenatal measurements of these chemicals parallelly with child adiposity assessments.
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