High levels of lead during pregnancy may lead to childhood obesity

October 8, 2019

A recently published study investigated whether maternal red blood cell (RBC) lead exposure is associated with intergenerational overweight and or obesity (OWO).

Although pediatric lead screening typically occurs at the 1-year well-child care visit, data on the extent of maternal lead exposure and its long-term consequences for child health are lacking. A recently published study in JAMA Network Open investigated whether maternal red blood cell (RBC) lead exposure is associated with intergenerational overweight and or obesity (OWO). The study also examined whether adequate maternal folate status is associated with reduced risk of OWO.

The National Institute of Health-funded prospective birth cohort study included 1,442 mother-child pairs who were recruited at birth between 2002 and 2013. The mean (SD) ages of the mothers and children were 28.6 (6.5) years and 8.1 (3.1) years, respectively, and 50.1% of the children were boys. The authors used child body mass index (BMI) z score, which was calculated according to US national reference data. OWO was defined as BMI at or greater than the 85th percentile for age and sex. Maternal RBC lead levels were measured from samples obtained 24 to 72 hours after delivery. The RBC lead level of a child was measured from the first pediatric lead screening.

Among the mothers in the study cohort, the median maternal RBC lead level and plasma folate levels were 2.5 (IQR 1.7-3.8) µg/dL and 32.2 (IQR, 22.1-44.4) nmol/L, respectively. Median child whole-blood lead level and child BMI z scores were 1.4 (IQR, 1.4-2.0) µg/dL and 0.78 (IQR –0.08-1.71), respectively. Mothers with the highest RBC lead levels were older, multiparous, more likely to be black, nonsmokers, had lower plasma folate levels, and were more likely to have prepregnancy OWO and diabetes. (According to the Centers for Disease Control and Prevention, a blood lead level of 0.92 µg/dL is typical in most adults in the United States. The level in pregnant women and in children should not exceed 5 µg/dL.)

The authors found that maternal RBC lead level was associated with child OWO risk in a dose-response fashion, with an odds ratio (OR) of 1.65 (95% CI 1.18-2.32) for high maternal RBC lead level (≥ 5.0 µg/dL) compared with low maternal RBC lead level (< 2.0 µg/dL). Child OWO was highest among children of OWO mothers with high RBC lead levels (adjusted OR 4.24, 95% CI 2.64-6.82) compared with children whose mothers were not OWO and had low RBC lead levels.

The authors also noted the association between maternal RBC lead levels and child BMI z scores differed according to maternal folate status among OWO mothers. Children of OWO mothers with high RBC lead levels had a ß(SE) of 0.31 (0.13) decrease in BMI z scores and 41% lower OWO risk (OR, 0.59; 95% CI 0.36-0.95) if their mothers had adequate plasma folate levels (≥ 20.4 nmol/L) compared with their counterparts.

Based on their findings, the authors believe that, in this sample of a US urban population, elevated maternal lead exposure was associated with an increased risk of intergenerational OWO independent of postnatal blood lead levels. However, their findings also indicate that folate plays a role in lowering OWO risk. While more research is needed to confirm these findings, ob/gyns may want to consider focusing on a combination of prenatal lead screening and optimal maternal folate nutrition for at-risk patients.