Maternal lead exposure may contribute to the risk for overweight or obesity in offspring across multiple developmental stages, but adequate maternal folate status can mitigate this association, according to study results published in JAMA Network Open.
As bone lead stores persist for years, there is a risk for continued exposure to lead long after exposure to external sources. Previous studies have reported that maternal exposure to lead impairs maternal health and infant neurodevelopmental outcomes. The goal of the current study was to explore the association between maternal lead exposure with intergenerational overweight/obesity risk and the significance of adequate maternal folate status in this relationship.
The prospective birth cohort study included mother-child pairs from the Boston Birth Cohort who were recruited at birth from October 2002 to October 2013. Maternal lead levels were measured using inductively coupled plasma mass spectrometry in red blood cell (RBC) samples obtained 24 to 72 hours after delivery. Maternal plasma folate levels were measured using chemiluminescent immunoassay in archived plasma samples, also obtained 24 to 72 hours after delivery.
The study sample included 1442 mother-child pairs (mean age of mothers, 28.6±6.5 years; mean age of children, 8.1±3.1 years). Median child body mass index (BMI) z score was 0.78 (interquartile range [IQR], -0.08 to 1.71). The median maternal RBC lead level was 2.5 μg/dL (IQR, 1.7-3.8 μg/dL) and the median maternal plasma folate level was 14.21 ng/mL (IQR, 9.75-19.59 ng/mL).
Maternal RBC lead levels were positively associated with child whole-blood lead levels, BMI z scores, and overweight/obesity risk. After adjusting for multiple potential confounders, the risk for overweight/obesity was higher in children born to mothers who had RBC lead levels in the range of 2.0 to <5.0 μg/dL (odds ratio [OR], 1.35; 95% CI, 1.05-1.72) and ≥5.0 μg/dL (OR, 1.65; 95% CI, 1.18-2.32) compared with children whose mothers had RBC lead levels <2.0 μg/dL.
The combination of the presence of overweight/obesity and high RBC lead levels (≥5.0 μg/dL) in mothers was associated with a more than 4-fold increased overweight/obesity risk in offspring (OR, 4.24; 95% CI, 2.64-6.82) compared with children born to mothers without overweight/obesity who had low RBC lead levels (<2.0 μg/dL).
Maternal folate status in mothers with overweight/obesity had a significant impact on the association between maternal RBC lead levels and child BMI z scores, as children born to mothers with high RBC lead levels and adequate plasma folate levels (≥9 ng/mL) had lower overweight/obesity risk (OR, 0.59; 95% CI, 0.36-0.95) compared with their counterparts.
The researchers acknowledged several study limitations, including only a single measurement of maternal lead exposure and folate levels, no data on dietary intake and physical activity in the children, and a predominantly urban low-income minority population in the United States, which may limit generalizability.
“[A] combination of prenatal lead screening and optimal maternal folate nutrition may inform a new public health strategy to identify and decrease intergenerational lead toxic effects and [overweight or obesity] risk among US urban low-income populations, beginning in the most sensitive in utero developmental period,” wrote the researchers.
Wang G, DiBari J, Bind E, et al. Association between maternal exposure to lead, maternal folate status, and intergenerational risk of childhood overweight and obesity. JAMA Netwk Open. 2019;2(10):e1912343.