New study links prenatal chemical exposure to childhood obesity trajectories

A recent study, published in Environmental Health Perspectives, assessed the connections between prenatal exposure to endocrine-disrupting chemicals (EDCs) and the growth patterns of children's body mass index (BMI) using single exposure and mixture modeling methods.

Study: Prenatal Exposure to Multiple Endocrine-Disrupting Chemicals and Childhood BMI Trajectories in the INMA Cohort Study. Image Credit: fizkes/Shutterstock.com

Background

Endocrine-disrupting chemicals (EDCs) have gained substantial research attention, as they are widely distributed and play a significant role in disrupting normal human growth, both before and after birth.

This study investigates how exposure to these chemicals may impact children's BMI growth rates, utilizing various approaches to consider both individual and concurrent exposures.

Early-life growth significantly influences long-term health, as overweight and obese children are more prone to excessive weight gain in adulthood, elevating the risk of diabetes, cardiovascular diseases, and premature mortality.

EDCs, found in plastics, cosmetics, food, and water, pose potential risks to childhood growth. These chemicals are either persistent, accumulating in the environment and increasing in concentration up the food chain, or nonpersistent, yet widely used, leading to continued exposure.

During pregnancy, these substances can cross the placenta, modifying the fetal hormonal environment, potentially increasing the risk of later-life chronic diseases. While previous studies have attempted to establish associations, most focused on one or two EDC categories or measured growth at a single point.

This study aims to explore growth dynamically, with a focus on multiple growth measures, particularly during the first two years of life, a period of rapid growth. Researchers used data from the INfancia y Medio Ambiente (INMA) cohort, which tracked nearly 2,000 individuals in a Spanish birth cohort, monitoring their BMI after exposure to EDCs.

The study examined various EDCs, including persistent EDCs like hexachlorobenzene (HCB), 4-4′-dichlorodiphenyldichloroethylene (DDE), polychlorinated biphenyls (PCB-138, -150, and -180), four perfluoroalkyl substances (PFAS), and nonpersistent EDCs/metabolites, encompassing eight phthalate metabolites and seven phenols.

Researchers traced BMI trajectories from birth to nine years of age and analyzed these graphs for associations with single and mixed exposures.

Study findings

The analysis revealed significant associations between single exposures to several EDCs (HCB, DDE, PCBs, and perfluorononanoic acid [PFNA]) and a distinct pattern of smaller birth size followed by a faster increase in BMI (trajectory 3), compared to a reference trajectory (trajectory 4) starting with an average birth size and a slower BMI gain.

This BMI increase was in the range of 20-30%. A doubling of PFNA exposure in utero led to a 32% higher risk of trajectory 3, compared to 20% for DDE and 25% for HCB. Sex-specific differences were observed, with an increase of 26% to 30% in trajectory risk in males exposed to HCB, DDE, and PCB-153, and in females for HCB.

HCB and DDE exposure alone also resulted in a significant risk increase of 15% for another trajectory (trajectory 1), characterized by a larger birth size followed by a faster BMI increase.

In males, DDE exposure was associated with a 20% higher odds of this trajectory. Among children in the middle socioeconomic stratum, HCB exposure increased the risk of either trajectory (1 or 3) by over 50%.

For children from low and high socioeconomic backgrounds, DDE exposure was linked to 40% and 23% higher risk for trajectories 3 and 1, respectively. PCB-associated risk for trajectory 3 was higher among wealthier children, with increases of 40% for PCB-138 and nearly 50% for PCB-153.

Among children from poorer backgrounds, PFNA exposure was associated with a 50% increased risk for trajectory 3. Considering the mixture model, there was an association with trajectory 3, with a 70% higher odds for each quintile increase in exposure to the mixture. HCB, DDE, and PCBs contributed significantly to this risk.

The mixture also showed an almost 60% increase in risk for trajectory 2 in females, characterized by larger birth size and slower weight gain afterward. Among disadvantaged children, the risk more than doubled for trajectory 3.

Implications

"This study provides evidence that prenatal EDC exposure, particularly persistent EDCs, may lead to BMI trajectories in childhood characterized by accelerated BMI gain."

The results support the association between HCB, DDE, PCBs, and an increased rate of BMI growth.

Additionally, the study establishes this association for the first time between BMI trajectories and PFAS, particularly PFNA, supporting previous research that linked these chemicals to childhood obesity.

Earlier studies suggested a slower BMI increase following EDC mixture exposure, possibly due to differences in sample populations, chemicals measured, follow-up age, growth parameters, and statistical methods.

Moreover, children from lower socioeconomic backgrounds exhibited a higher risk with some EDCs, suggesting increased vulnerability to these chemicals for reasons yet unknown. Further studies are required to confirm and explain these findings.

"Given that ours are the first studies to analyze EDC mixtures with growth trajectories, it is important for the findings to be replicated in other studies."

Written by

Dr. Liji Thomas

Dr. Liji Thomas is an OB-GYN, who graduated from the Government Medical College, University of Calicut, Kerala, in 2001. Liji practiced as a full-time consultant in obstetrics/gynecology in a private hospital for a few years following her graduation. She has counseled hundreds of patients facing issues from pregnancy-related problems and infertility, and has been in charge of over 2,000 deliveries, striving always to achieve a normal delivery rather than operative.