Effect of subsequent pregnancies on the risk of developing diabetes following a first pregnancy complicated by gestational diabetes: a population-based study

Aims — Women with gestational diabetes mellitus have a high risk of developing Type 2 diabetes, secondary to post-partum progression of the chronic pancreatic beta-cell defect that underlies their presenting with dysglycaemia in pregnancy. Insulin-sensitizing therapy can decrease this risk of Type 2 diabetes, partly by offloading the secretory demand placed on the beta-cells. Conversely, however, it is not known whether the considerable secretory demands posed by the physiologic insulin resistance of a subsequent pregnancy could accelerate the progression to Type 2 diabetes. Thus, the authors sought to determine whether subsequent pregnancies are associated with the risk of developing diabetes following gestational diabetes.

Methods — Using a population-based administrative database, we identified all women in Ontario, Canada, whose first pregnancy was between April 2000 and March 2007 and was complicated by gestational diabetes (n=16,817). This cohort was followed for a median 4.5 years for subsequent pregnancies and the development of diabetes.

Results — During follow-up, 2,731 women (16.2%) developed diabetes. Gestational diabetes recurred in 41.5% of subsequent pregnancies. Interestingly, after covariate adjustment, a subsequent pregnancy was associated with a reduced risk of diabetes (adjusted hazard ratio (HR)=0.68, 95% CI 0.60–0.76; P<0.0001). Specifically, whereas each subsequent gestational diabetes pregnancy was associated with a modestly increased risk of diabetes (adjusted HR = 1.16, 95% CI 1.01–1.34; P=0.03), each non-gestational diabetes pregnancy was associated with a significantly reduced risk of diabetes (adjusted HR=0.34, 95% CI 0.27–0.41; P<0.0001).

Conclusions — A subsequent pregnancy is not necessarily associated with an increased risk of Type 2 diabetes following gestational diabetes. Instead, the absence of recurrent gestational diabetes in a subsequent pregnancy may identify a lessened risk of developing Type 2 diabetes in this high-risk patient population.