Carrying a Boy May Increase Mom’s Risk of Gestational Diabetes

With commenary by Baiju Shah, MD, PhD, associate professor of medicine, University of Toronto

Women who develop gestational diabetes mellitus—diabetes that occurs during pregnancy—are at greater risk of gestational diabetes in their next pregnancy. Having gestatational diabetes also puts you at risk for type 2 diabetes. Yet, predicting who will develop either type of diabetes has been difficult. Research has pointed to certain risk factors including ethnicity, age, obesity, and infant birth weight. Now a new study, published in the Journal of Clinical Endocrinology and Metabolism, has found that the gender of the baby is a risk factor as well.

Gestational diabetes mellitus (GDM) is caused by a defect in pancreatic β-cells, reducing their ability to produce enough insulin to compensate for insulin resistance, which typically occurs in the second half of a woman’s pregnancy.  Insulin resistance occurs in all pregnant women, but those whose bodies can’t produce enough insulin will develop GDM.

The laregescale study of more than 640,000 pregnancies, found that women carrying a boy had a slightly increased risk of GDM. “We hypothesize that pregnancy with a boy leads to worse pregnancy-associated metabolic changes than pregnancy with a girl—this is why we see a higher rate of GDM in women carrying a boy,” says the study’s lead author, Baiju Shah, MD, PhD, associate professor of medicine, University of Toronto.

 “Male fetuses seem to impact the mother’s metabolism—specifically, her pancreatic β-cells’ ability to produce insulin—more than female fetuses do,” he says. “But how the fetus causes this impact on the mother’s metabolism is not understood.”

Interestingly, the study found that if a woman had GDM in her first pregnancy, having a boy had no effect on her risk of having GDM in subsequent pregnancies. That’s probably because women with GDM in their first pregnancy are at such a high risk of having GDM again in the second pregnancy—around 40 percent—that the effect of the baby’s gender doesn’t make much difference, says Dr. Shah.

On the other hand, women who had GDM in their first pregnancy had a greater risk of developing type 2 diabetes post pregnancy if they had a girl. This suggests that these women likely have overall poorer metabolic functions to begin with since they developed GDM despite not carrying the “riskier” boy. This underlying risk puts them at increased risk of type 2 diabetes after the pregnancy.

The study adds to the literature about risk of gestational diabetes in women. “I think it’s worthwhile for women and their obstetricians to recognize that although we often worry about how the mother’s health and behaviors can impact the baby, we perhaps need to start thinking about how the baby can affect the mother’s health,” says Dr. Shah.

Women carrying boys should be aware of their increased risk of GDM. And women who had GDM and carried a girl through pregnancy may want to be more vigilant post-delivery and focus more on reducing their risks of type 2 diabetes through eating healthy, exercising and maintaining a healthy weight.  

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