Mother's Pre-Pregnancy BMI May Play a Role in Childhood Cancer Risk

Pre-pregnancy body mass index (BMI) of mothers may be linked to cancer risk in their children, according to study findings published in the American Journal of Epidemiology.

A team of researchers from the University of Pittsburgh Graduate School of Public Health and UPMC Hillman Cancer Center examined the associations of maternal characteristics, before pregnancy and at delivery, and the risk of any childhood cancer, including leukemia. They searched more than 1.8 million birth records in the state of Pennsylvania from 2003 to 2015, including nearly 2,500 cases of childhood cancer diagnosed from 2003 to 2016.

“We know that any exposure that can affect the mom or the fetus during a pregnancy might be important for the child’s health later, since that is a very sensitive time for exposure and development,” lead author Shaina Stacy, who holds a doctorate in environmental and occupational health and is a postdoctoral scholar in the Pitt Public Health Department of Epidemiology and UPMC Hillman Cancer Center, said in an interview with CURE®. “Maternal pre-pregnancy obesity was something we were interested in due to the rise in obesity in the United States and since obesity has been linked to increased risk for some adult cancers.”

The researchers found a correlation between women considered to be obese based on their BMI and the likelihood of their sons or daughters to develop cancer in early childhood, even after correcting for risk factors, such as the size of the newborn and age of the mother. The Centers for Disease Control and Prevention classifies obese as those with a BMI of 30 or greater.

In the study, children born to mothers with a BMI above 40, which is considered severely obese, had a 57% higher risk of developing leukemia and a 59% higher risk of developing acute lymphoblastic leukemia before they were 14 years old compared with children born to mothers with BMIs between 18.5 and 24.9, whose weight is considered normal. These children also had a 32% higher risk of developing any cancer. The risk of leukemia was 46% higher for children born to mothers weighing between 198 and 218 pounds, and 42% higher for children born to mothers weighing more than 220 pounds. For children under 5, the risk of any leukemia was 77% higher if their mothers were in the highest BMI group. Maternal height was not associated with risk, except that the risk of leukemia among 5-14-year-olds was 89% higher for those born to the tallest moms compared to children of average-height moms.

“We can only speculate (about the correlation between mother’s BMI and children’s cancer) at this point. One (possible) reason is disruptions or imbalances in the mother’s insulin levels and imbalances in insulin-like growth factors, which have been linked to obesity and increased risk in adult cancers,” Stacy said. “Another potential factor is changes in gene expression in the mother that could be inherited by the child.”

Obesity is a potentially modifiable risk factor, Stacy explained. “It’s very important for women and pregnant women to talk to their doctors first to get advice on what’s good for their individual health,” she said. “I think what’s promising for our study is we see lower risk with lower BMIs, so to me that translates to (the idea that) even small reductions in body mass index, whether that’s pre- or during pregnancy, could translate to reductions in risks for cancer in children.”

The researchers hope their findings will lead to a policy-level intervention — for example, Stacy said, an increase in the number of safe spaces for exercise or increased access to healthy foods.

“Obesity has been linked to other health outcomes and so we are hoping these findings can point to one additional reason for weight loss, which is not just healthy for moms but also their babies, too,” Stacy said.