Obesity in pregnant women can lead to lower IQ and impaired development in boys later, study shows
A mother's obesity in pregnancy can negatively affect the child's development years down the road, according to researchers, who found that prepregnancy overweight and obesity were associated with lower IQ among boys at 7 years of age.
The researchers from the University of Texas at Austin, and Columbia University, found impaired motor skills in preschoolers and lower IQ in middle childhood for boys whose mothers were severely overweight while expecting them. The researchers did not find any effect on girls.
"These findings are important considering overweight and obesity prevalence and the long-term implications of early cognitive development," says the team in their findings. The researchers studied 368 mothers and their children, all from similar economic circumstances and neighborhoods, during pregnancy and when the children were 3 and 7 years of age. Overweight affected 23.9% of mothers and obesity affected 22.6%.
At age 3, the researchers measured the children's motor skills and found that maternal obesity during pregnancy was strongly associated with lower motor skills in boys. At age 7, they again measured the children and found that the boys whose mothers were overweight or obese in pregnancy had scored 5 or more points lower on full-scale IQ tests, compared with boys whose mothers had been at a normal weight.
"At child age 7, IQ and working memory scores were higher among girls compared to boys. Specifically, in boys, maternal overweight and obesity were associated with lower fullscale IQ and perceptual reasoning scores at child age 7, while maternal overweight was associated with lower processing speed scores," say the study.
“What's striking is, even using different age-appropriate developmental assessments, we found these associations in both early and middle childhood, meaning these effects persist over time," says Elizabeth Widen, assistant professor of nutritional sciences at UT Austin, in the analysis published in BMC Pediatrics.
The team of nutrition and environmental health researchers found that the differences are comparable to the impact of lead exposure in early childhood. A previous study had suggested that boys whose mothers had fluoride during pregnancy scored lower on an IQ assessment. Another found lower performance IQ in boys, but not girls, whose mothers were exposed to lead.
Widen emphasizes that the current study findings are not meant to shame or scare anyone. “We are just beginning to understand some of these interactions between mothers' weight and the health of their babies," says Widen, adding that women need to work with their doctors and talk about what is appropriate for their circumstances.
According to the US Centers for Disease Control and Prevention (CDC), the prevalence of obesity among US adults was 39.8%, and affected about 93.3 million in 2015~2016. An estimated 36.5% women in the 20-39 age group were obese in the US in 2015-2016, as compared to 44.7% women in the 40-59 age group.
While previous research has found links between a mother’s diet and cognitive development -- such as higher IQ scores in children whose mothers have more of certain fatty acids found in fish -- it is not yet clear why obesity in pregnancy would affect a child later.
According to the researchers, dietary and behavioral differences may be driving factors. They say fetal development might be affected by some of the things that tend to happen in the bodies of people with too much extra weight, such as inflammation, metabolic stress, hormonal disruptions and high amounts of insulin and glucose.
The researchers controlled for several factors in their analysis, including race and ethnicity, marital status, the mother's education and IQ, as well as whether the children were born prematurely or exposed to environmental irritants such as air pollution. What the pregnant mothers ate or whether they breastfed were not included in the analysis.
The “nurturing environment” at home in early childhood was also examined and accounted for in the analysis. The researchers looked at how parents interacted with their children and whether the child was provided with books and toys. A nurturing home environment was found to lessen the negative effects of obesity, says the study.
"The effect on IQ was smaller in nurturing home environments, but it was still there," says Widen.
Since childhood IQ is a predictor of education level, socio-economic status and professional success later in life, the researchers said there is potential for effects to last into adulthood. Based on their findings, the researchers have advised women, who are obese or overweight, to eat a well-balanced diet that is rich in fruits and vegetables when they become pregnant and take a prenatal vitamin, besides staying active and making sure to get enough fatty acids such as the kind found in fish oil.
Giving children a nurturing home environment also matters, as does seeing a doctor regularly, including during pregnancy to discuss weight gain, say the researchers in their recommendations.