Lifestyle and environment more likely to affect a child’s BMI than mum’s weight during pregnancy

Interesting new findings relevant to the LongITools project

Press Release by University of Bristol

Researchers from the University of Bristol and Imperial College London have found that a high Body Mass Index (BMI) of a mother before and during pregnancy is not a major cause of high BMI in their offspring – indicating that childhood and teen obesity is more likely to be a result of the interaction between genetic and lifestyle factors.

The study, published in BMC Medicine, used data from two longitudinal studies – Children of the 90s (also known as the Avon Longitudinal Study of Parents and Children) based at the University of Bristol, and Born in Bradford based in Bradford.

It is known that greater maternal BMI before or during pregnancy is associated with a higher BMI in children, however the extent to which the mother’s weight causes obesity in childhood, or whether this is caused by environmental and lifestyle factors post conception and birth is unclear.

The research team from the University of Bristol used a method called Mendelian randomisation, which measures variation in genes to infer the effect of an exposure (in this case maternal BMI) on an outcome (i.e. offspring BMI). They looked at birthweight and BMI at age 1 and 4 years in both Children of the 90s and Born in Bradford participants, and then also BMI at age 10 and 15 years in just the Children of the 90s participants. They found that there was a moderate causal effect between maternal BMI and the birth weight of children, however in most older age groups they did not find a strong causal effect.

Lead author Dr Tom Bond, Senior Research Associate at the University of Bristol and Visiting Researcher at Imperial College London, explained: “We found that if women were heavier at the start of pregnancy this isn’t a strong direct cause of their children being heavier as teenagers. This is important to know.”

Professor Sylvain Sebert, LongITools Coordinator and an author on the paper, commented on these findings:

“This work from many of our close collaborators is very interesting as it is important to understand that an individual’s health is the consequence of multiple causes. Therefore, it will be vital to broaden the work to investigate the exposome context and to improve our understanding of causality, especially when addressing early signs of heart disease risk.”

Paper: Exploring the causal effect of maternal pregnancy adiposity on offspring adiposity: Mendelian randomization using polygenic risk scores.
https://doi.org/10.1186/s12916-021-02216-w