Carrying a Boy Ups Gestational Diabetes Risk in Large Cohort

May 26, 2015

Whereas a pregnant mother's health is known to affect the health of her developing baby, new research suggests that the baby can also affect the mother's health.

Specifically, the sex of the fetus appears to be linked to whether a pregnant woman develops gestational diabetes in a first pregnancy and, if she has gestational diabetes, whether she will subsequently develop type 2 diabetes.

In a retrospective, decadelong study of virtually all pregnant women in the province of Ontario, Dr Ravi Retnakaran (Mount Sinai Hospital, Toronto, ON) and Dr Baiju R Shah (Sunnybrook Health Sciences Centre, Toronto, ON) found that the risk of developing gestational diabetes was increased by 3% in women who were carrying a boy.

"The differences are so small that it's probably not going to make a difference for screening [for gestational diabetes]," Dr Shah told Medscape Medical News. However, this study sheds light on the ways that pregnancy and maternal diabetes are connected and how babies affect mothers' health (as well as vice versa), he summarized.

The study was published online May 20, 2015 in the Journal of Clinical Endocrinology & Metabolism.

Fetal Sex and Maternal Diabetes

In a previous, smaller study, the researchers showed that pregnant women who were carrying a boy were more likely to develop gestational diabetes (Diabetes Care. 2015;38:844–851). In this study, they aimed to determine whether the sex of the fetus was associated with the mother's risk of developing type 2 diabetes after delivery or of developing gestational diabetes in a subsequent pregnancy.

Drs Retnakaran and Shah analyzed data from provincial health-insurance claims from women in Ontario who were aged 15 to 49 and had a singleton first pregnancy between April 2000 and March 2010.

About half of the women delivered a girl (313,280) and the rest delivered a boy (329,707). A small percentage (3.6%) of the women had gestational diabetes. The population was followed for a median of 3.8 years.

During this time 16,272 women were diagnosed with type 2 diabetes, prior to any subsequent pregnancy, and 39.5% of women who had gestational diabetes in a first pregnancy also had it in a second pregnancy.

The research revealed three main findings.

First, as shown in the earlier smaller study, having a male fetus was a risk factor for developing gestational diabetes. Women who delivered a boy had a higher risk of gestational diabetes in the first pregnancy (odds ratio [OR], 1.03). Moreover, women who delivered a boy also had a higher risk of gestational diabetes in a second pregnancy (OR, 1.04).

Second, among the women who had gestational diabetes during the first pregnancy, those who had delivered a girl had a higher risk of developing type 2 diabetes (OR, 1.07). These women probably had poorer beta-cell function, since they still developed gestational diabetes even in the absence of the adverse metabolic effect from having a male fetus, the authors speculate.

Third, among women with who did not have gestational diabetes during their first pregnancy while carrying a girl, having a boy in their second pregnancy predicted an increased risk of gestational diabetes (OR, 1.07). This reinforces the original finding that having a boy ups the risk of gestational diabetes, whereas having a girl does not, say the researchers.

But they acknowledge that they did not have any data for the beta-cell function in these mothers, which is a study limitation.

Nevertheless, the study shows that the "sex of the baby and maternal [gestational diabetes] status can together provide insight into a woman's risk of diabetes after delivery and in a subsequent pregnancy," Drs Retnakaran and Shah write.

"Fetal sex thus emerges as a previously unrecognized factor associated with the natural history of maternal diabetic risk both after delivery and in a subsequent pregnancy."

The study was funded by the Institute for Clinical Evaluative Sciences and the Ontario Ministry of Health and Long-Term Care. The authors have no relevant financial relationships.

J Clin Endocrinol Metab. 2015. Published online May 20, 2015. Abstract

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