New US research has found that boys born to mothers who were obese while pregnant appear to have lower motor skills at age three and a lower IQ at age seven.
The new study by researchers at The University of Texas at Austin and Columbia University looked at 368 mothers and their children, and asked the women to self-report their weight during the second and third trimesters of pregnancy.
The researchers also tested the children's motor skills and IQ level at ages three and seven.
The findings, published in BMC Pediatrics, showed that boys whose mothers had been obese during pregnancy had lower motor skills at age three.
In addition, those whose mothers had been overweight or obese in pregnancy had scores 5 or more points lower on full-scale IQ tests at age seven, compared with boys whose mothers had been at a normal weight.
"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," said author Elizabeth Widen.
"These findings aren't 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."
The findings held true even after taking into account factors such as the mother's education and whether the children were born prematurely.
However, when the researchers looked at how nurturing the child's environment was at home, for instance, how parents interacted with their children and whether the child was given books and toys, they found that a nurturing home environment could reduce the negative effects of maternal obesity, though Widen added that, "The effect on IQ was smaller in nurturing home environments, but it was still there."
Being obese while pregnant appeared to have no effect on a daughter's motor skills development or IQ.
The researchers pointed out that this is not the first study to conclude that what a mother is exposed to in pregnancy appears to affect sons more than daughters.
They noted that a 2018 study found that mothers' exposure to lead during pregnancy appeared to lower IQ in the case of boys, but not girls.
A 2019 study found that boys whose mothers were exposed to fluoride in pregnancy also scored lower on an IQ assessment.
Widen advised women who are obese or overweight when they become pregnant to eat a well-balanced diet high in fruits, vegetables and fatty acids from fish, take a prenatal vitamin, keep active and make sure to see a doctor during pregnancy to discuss weight gain.
"Work with your doctor and talk about what is appropriate for your circumstances," Widen said.