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Type 2 Diabetes Risk for Women With Gestational Diabetes is Increased by Genetic Factors

NEW YORK – Women who experienced gestational diabetes are more likely to develop type 2 diabetes later on if they also have genetic risk factors for the disease, a new study has found.

Gestational diabetes, a condition in which women have high blood sugar levels during pregnancy, affects between 6 percent and 15 percent of pregnancies worldwide. While the condition typically resolves itself after the baby is born, women who have experienced gestational diabetes have a sevenfold increased risk of developing type 2 diabetes than those who did not. More than 40 percent of women with a history of gestational diabetes develop type 2 diabetes within 10 years.

A team led by researchers at the Eunice Kennedy Shriver National Institute of Child Health and Human Development sought to gauge whether genetic risk scores could distinguish women with a history of gestational diabetes who develop type 2 diabetes from those who do not. They applied this score to two population cohorts, one from the US and one from Denmark, to find that women with high genetic risk scores were more likely to go on to develop type 2 diabetes. Their findings also indicated that eating healthy could mitigate some of that risk.

"Our study suggests that a healthful diet may reduce risk among women who have had gestational diabetes and are genetically susceptible to type 2 diabetes," senior author Cuilin Zhang from NICHD said in a statement. "However, larger studies are needed to validate these findings." 

The results were published today in BMJ Open Diabetes Research & Care

Based on recent genome-wide association studies in European populations, the researchers identified 59 SNPs associated with type 2 diabetes risk that they bundled into a genetic risk score for the condition. 

They then genotyped 2,434 white women with a history of gestational diabetes from the US Nurses' Health Study II and the Danish National Birth Cohort and determined their genetic risk scores. Of the women in the study, 601 developed type 2 diabetes during the median follow-up period of 21 years for the US cohort and 13 years for the Danish cohort.

A high genetic risk score was associated with increased risk of developing type 2 diabetes in both the US and Danish cohorts. When broken up by quartiles, the highest-scoring group was 19 percent more likely to develop type 2 diabetes than the lowest scoring group.

Every five risk alleles were associated with a 7 percent increase in type 2 diabetes risk in the US cohort and 9 percent increase in risk in the Danish cohort.

This association between a history of gestational diabetes and genetic risk of type 2 diabetes was stronger among women with poorer diets. Though the researchers noted that the interaction was not significant, it was consistent in both cohorts. They reported that women with poor diets and a high genetic susceptibility to type 2 diabetes were 29 percent more likely to develop the condition than those with healthier diets.

This suggested that post-delivery interventions might have the potential to prevent type 2 diabetes in this population. The finding, the researchers wrote in their paper, "supports public health efforts of encouraging a healthful diet to prevent T2D among the high-risk population — women with a history of [gestational diabetes]."

They additionally noted that the link between genetic risk score and type 2 diabetes didn't vary with other factors they examined in the women with a history of gestational diabetes, including pre-pregnancy BMI, family history of diabetes, and post-pregnancy physical activity.