Findings from researchers at the University of Bristol and Imperial College London show that a mother’s BMI before and during pregnancy does not have a substantial role in her child’s BMI, suggesting that childhood and teen obesity is more likely the result of lifestyle factors.

Children of the 90s (also known as the Avon Longitudinal Study of Parents and Children), headquartered at the University of Bristol, and Born in Bradford, based at Bradford Teaching Hospitals NHS Foundation Trust, were included in the study, which was published today in BMC Medicine.

Although it is well established that a higher maternal BMI before or during pregnancy is linked to a higher BMI in children, it is unknown to what degree the mother’s weight causes childhood obesity, or whether this is caused by environmental and lifestyle variables after conception and birth.

The researchers used a method called Mendelian randomisation, which examines gene variation to estimate the impact of an experience on an outcome.

They looked at birthweight and BMI at ages 1 and 4 in both Children of the 90s and Born in Bradford participants, as well as BMI at ages 10 and 15 in just the Children of the 90s.

They discovered a moderate causal impact between mother BMI and child birth weight, but they did not detect a robust causal effect in most older age groups.

They discovered that a woman’s weight at the beginning of pregnancy isn’t a good predictor of her child’s weight as a teenager.

According to Dr. Tom Bond, the lead author of the study, “this is important to know. Supporting women and men at all ages to keep a healthy weight will be needed to prevent obesity. It isn’t enough to just focus on women entering pregnancy. Despite this, there is good evidence that maternal obesity causes other health problems for mothers and babies (aside from offspring obesity).”

The study recommends mothers should still be encouraged and supported to maintain a healthy weight.

“It will be important to broaden this work to investigate other characteristics of mothers and fathers during pregnancy and a child’s early life that might affect children’s weight, and also to look at the offspring when they are in adulthood and are old enough to begin showing early signs of heart disease risk.”

Source: 10.1186/s12916-021-02216-w

Image Credit: Getty

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