New study gets beyond BMI in pregnancy to gauge child’s risk of obesity

Obesity and diabetes in mothers have traditionally been considered risk factors for the child to also develop obesity. But a new study suggests that more narrow measures of health during pregnancy could help better assess that risk.

Researchers grouped pregnant women based on specific metabolic traits and found that insulin resistance was associated with the highest risk, compared with other traits such as high cholesterol and triglycerides, according to a study published in JAMA Network Open on Tuesday.

The risk linked to insulin resistance was even higher than that associated with prepregnancy obesity, defined as a body mass index over 30, and with diabetes diagnosed in gestation, the study said.

There’s a growing movement in the medical community to move away from broad measures such as BMI, since they may not accurately predict people’s health risks and there may be other measures that are more useful in guiding treatment plans for patients.

“What we were able to do was group women who are more metabolically similar versus group women based on similarities in size,” said Ellen Francis, the lead author and a postdoctoral fellow at the University of Colorado Anschutz Medical Campus. “If we’re interested in the risk of obesity that’s attributable to pregnancy, we probably need to start thinking a little beyond” BMI and gestational diabetes.

The researchers analyzed the histories of 1,325 women and were able to track  727 of their children for approximately 5 years. They used a clustering algorithm to group pregnant women based on metabolic similarities, then looked at the risk of each group’s children developing obesity or a high percentage of fat mass.

They found that compared with a group of metabolically healthy women, the group of women with insulin resistance was linked to about a five-fold higher risk of obesity in children and nine-fold greater risk of high fat mass in children.

Meanwhile, women with both obesity and gestational diabetes were linked to about a four-fold greater risk of obesity in children compared with women who didn’t have those conditions.

The study suggests there are pregnant people who don’t have traditional risk factors but whose children would have higher risk of obesity. For example, in the group of women in the study who had insulin resistance, only 60% had prepregnancy obesity and just 15% of them had gestational diabetes.

“This is a great study that supports the importance of insulin resistance during pregnancy as one of the key determinants of metabolic ‘programming’ for risk of obesity in the offspring,” said Marie-France Hivert, an associate professor of population medicine at Harvard Medical School who was not involved in the work.  She added, “This study also highlights the heterogeneity of metabolic subtypes during pregnancy, and add to the literature supporting precision medicine approaches during pregnancy and beyond.”

Francis said she didn’t want clinicians to ignore BMI or gestational diabetes. But in the future as there are more efficient ways of measuring different metabolic traits, she said, “I think we need studies like this one to help guide what we might want to measure in addition to BMI and glucose.”

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