Boys born to obese mothers ‘have worse motor skills and at age 3 and lower IQ at age 7’

Boys born to obese mothers have worse motor skills and at the age of three and lower IQ at age seven, a study suggests.

Researchers studied 368 children’s intelligence found a ‘significant’ link with maternal obesity during pregnancy. This was only in boys. 

Obesity causes a number of changes in the body and scientists have suggested these also impact on fetal development.

They considered that hormone disruptions or mineral deficiency as a result of a mother’s obesity slow the child’s brain development down.

Boys born to obese mothers have worse motor skills and at the age of three and lower IQ at age seven, a study on children and mothers from New York City suggests

Co-author of the study Elizabeth Widen, assistant professor of nutritional sciences at The University of Texas at Austin, said the study was not to shame mothers.

She said: ‘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.

‘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.’

Researchers at UT Austin and Columbia University Mailman School of Public Health studied the children, from New York City, at two points – three and seven years of age.

At age three, the researchers measured the children’s motor skills, which would include coordination, dexterity, movement and speed.

Examples include throwing a ball or playing a musical instrument well – but it’s not clear how the researchers studied this.

Girls had higher scores compared to boys – an average of 102.3 compared with 97.2.


Being obese during pregnancy can have a major impact on mother and baby’s health.

It carries the risk of miscarriage, stillbirth, gestational diabetes in the mother, a difficult delivery and the baby suffering obesity later in life or having birth defects, the Mayo Clinic says.

Women are advised to lose weight before they become pregnant to protect their own and their baby’s health. 

If they are very overweight (usually defined as having a BMI of 30 or above) and pregnant, it is not recommended to try to lose weight during the pregnancy, as this may not be safe, according to the NHS.

There is no evidence that losing weight while pregnant will reduce the chance of complications.

The best way to protect the mother’s own health and her baby’s health is to go to all the antenatal appointments so that the midwife, doctor and any other health professionals can keep watch for complications. 

It’s also important to eat a healthy, balanced diet and get some physical activity every day. 

A healthy diet during pregnancy to give a baby plenty of nutrients includes eating plenty of fruit and vegetables, starchy and filling foods to avoid snacking, sources of protein, and dairy. It is advised to limit high fat and sugary foods to avoid putting on excess weight.

Boys whose mothers were obese during pregnancy had a lower score by around eight points compared to boys whose mothers were a healthy weight. 

These findings were published first in the Journal of Developmental Origins of Health and Disease in September 2019. 

At age seven, the researchers measured the children’s full-scale IQ. The findings are published in the journal BMC Pediatrics.

IQ ranges from 70 to 140, and the full-scale IQ incorporates verbal reasoning, working memory, processing speed and more. 

Findings show that boys whose mothers were overweight or obese in pregnancy had scores of five or more points lower on full-scale IQ tests, compared to boys whose mothers had been at a normal weight. 

The researchers said it’s only early research and the mechanisms behind the findings are not clear. 

They said the effects of obesity on the body may also impact on the foetus. 

People who are obese are more likely to suffer hormonal disruptions – such as high amounts of insulin – which may ‘adversely affect’ the placenta and therefore development during critical stages.

The placenta may also be disturbed by inflammation and metabolic stress, which is more commonly seen in people with obesity, known to fuel metabolic diseases such as type 2 diabetes. 

Fetal brain development may also be linked to the diet specifically -it’s possible those who are obese have a high-fat diet, depriving the baby of vitamins and nutrients, the team said.

Previous research has found a baby’s cognition is linked to what the mother eats. For example, eating fatty acids found in fish such as salmon during pregnancy has been linked with higher IQ scores in children.  

But the mother’s in this study were not asked about what they ate, or whether they breastfed. There is a long-standing debate about whether breast milk boosts a baby’s intelligence, so this may have been important for the findings.

The researchers controlled for several factors in their analysis which may have impacted the results, including the mother’s education and IQ, whether the children were born prematurely or exposed to air pollution.  

The team also examined and accounted for the nurturing environment in a child’s home, looking at how parents interacted with their children and if the child was provided with books and toys. 

A nurturing home environment was found to lessen the negative effects of obesity, but the boys’ IQ still remained lower.  

The research team advised women who are overweight during pregnancy to eat a well-balanced diet with an abundance of fruits, vegetables, fish oils and appropriate supplements. 

This is not the first study to find that boys appear to be more vulnerable than girls while developing in the womb. 

Evidence suggests boys and girls respond differently to adverse exposures, such as stress and toxins.