Maternal prepregnancy overweight and obesity were found to be associated with lower IQ scores in boys in low-income, multiethnic populations, according to study results published in BMC Pediatrics.

Prepregnancy body mass index (BMI) and gestational weight gain disproportionately affect low-income populations and are negatively associated with cognitive development in early childhood. The study researchers aimed to use data from a cohort of low-income African American and Dominican mother-child pairs in the Columbia Center for Children’s Environmental Health Mothers and Newborns study to identify sex-specific associations between maternal prepregnancy BMI, gestational weight gain, and early neurodevelopment.

A total of 368 mother-child pairs (55.2% female offspring) were followed from <20 weeks’ gestation to 7 years of age. Medical records were used to calculate maternal BMI and determine gestational weight gain from self-reported prepregnancy weights. At child age 7, the Wechsler Intelligence Scale for Children was administered to measure neurodevelopment across 4 cognitive indices, with an average expected score of 100±15. Additionally, an unstructured Home Observation for Measurement of the Environment (HOME) Inventory was performed at median child age of 3.6 years (range, 1.1-6.3 years) to assess the quality of the cognitive stimulation and emotional support in the home environment.

At age 7, IQ scores were higher among girls (99.7±11.6) than boys (96.9±13.3; P =.03). Among boys, IQ and perceptual reasoning scores were associated with maternal prepregnancy BMI, with higher scores observed for boys born to women with normal prepregnancy BMI. Maternal overweight and obesity were associated with lower full-scale IQ (overweight: effect size [β], -7.4 [P =.005]; obesity: β, -6.5 [P =.01]) and perceptual reasoning scores (overweight: β, -7.5 [P =.01]; obesity: β, -5.8 [P =.04]), and maternal overweight was associated with lower processing speeds (β, -8.9; P =.01). Maternal obesity was also associated with lower verbal comprehension scores (β, -4.6; P =.04). These associations were not seen among girls.

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Gestational weight gain was not associated with neurodevelopment in boys, but a limited association between perceptual reasoning and gestational weight gain was noted in girls.

The effects of prepregnancy BMI on IQ and verbal comprehension in boys were attenuated after adjustment for HOME scores. The effect size of maternal obesity on IQ was reduced to a β of -5.7 when adjusted for HOME score, reflecting a difference of 12%. Further, the association between prepregnancy obesity and verbal comprehension skills was lost entirely after adjustment for HOME score.

The researchers noted that the relatively small sample size may have limited the ability to detect effect measure modification, particularly after sex stratification. Additionally, the effect of other medical conditions such as preeclampsia or gestational diabetes could not be evaluated, as data for these were not included in the initial study design.

“In summary, we found that prepregnancy overweight and obesity were associated with lower IQ scores in boys at 7 years of age, but not in girls, an association that was partially attenuated by adjustment for the home environment,” the investigators concluded. “These findings are important in light of the high prevalence of maternal overweight and obesity, and the longer-term implications of early cognitive development.”

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Widen EM, Nichols AR, Kahn LG, et al. Prepregnancy obesity is associated with cognitive outcomes in boys in a low-income, multiethnic birth cohort. BMC Pediatr. 2019;19:507.