Sons Whose Mothers Were Obese During Pregnancy More Likely to Have Lower IQs, Study Finds

The cognitive health and development of boys may be impacted by their mothers' body mass index (BMI) while pregnant with them, according to research from Columbia University and the University of Texas at Austin. The study, which was published in the journal BMC Pediatrics on Friday, observed 368 subjects from a "low-income cohort of African American and Dominican women" during the second half of their pregnancies, and then evaluated their children three and seven years later. Researchers found that the sons of women whose BMIs indicated that they were overweight or obese when they became pregnant were more likely to show less developed motor skills as 3-year-olds and lower intelligence as 7-year-olds compared to boys whose mothers were at "normal" weights during pregnancy. Body mass index calculations use a person's height and weight to estimate what a healthy weight for them would be. In general, a BMI between 18.5 and 25 is considered "normal." Among the expectant mothers examined for this study, 23.9 percent were overweight, meaning they had BMIs between 25 and 29.9, and 22.6 percent had BMIs above 30 and were considered obese. Among boys, the study found, maternal overweight and obesity correlated with IQ scores between 4.6 and almost 9 points lower than those of boys whose mothers weights were in the "normal" range before pregnancy. Researchers did not observe the same phenomenon among daughters whose mothers had been obese. "These findings aren't meant to shame or scare anyone," Elizabeth Widen, assistant professor of nutritional sciences at UT Austin and one of the study's co-authors, said in a press release. "We are just beginning to understand some of these interactions between mothers' weight and the health of their babies." Newsweek has contacted the study's senior author for further comment.

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For the design of the study, researchers noted that "Maternal obesity and high gestational weight gain (GWG) disproportionally affect low-income populations." The study's subjects were all part of the urban birth cohort study at the Columbia Center for Children's Environmental Health in New York City. Researchers found that the correlation between obesity during pregnancy and lower cognitive development in boys persisted when controlling for a variety of other factors including race and ethnic background, the mother's IQ and educational attainment, marital status and the level of interaction the mother had with her child. Why maternal obesity appeared to affect childhood IQ was unclear, but earlier research has suggested that there is a relationship between a mother's diet and her child's later IQ, according to Columbia University. Researchers did not control for what the mothers ate, the press release noted. The study's authors wrote that because childhood IQ has been shown to be an indicator of later success in life, studying how a mother's obesity could affect the IQ of her child is worthwhile. "These findings are important in light of the high prevalence of maternal overweight and obesity, and the longer-term implications of early cognitive development," they concluded. The recent findings support earlier research on obesity and pregnancy. A 2008 report by the National Institutes of Health linked maternal obesity to a variety of negative outcomes, including increased risks to the mother's health, as well as increased likelihood of miscarriage, stillbirth and conditions such as spina bifida, neural tube defects and congenital heart disease. Obesity has remained a health problem of epidemic proportions across the United States for over a decade. As Newsweek reported earlier in December, another recent study warned that half of all U.S. adults could be obese by 2030.