Postpartum prevention
The DPP demonstrated, moreover, that intensive lifestyle therapy and metformin not only were both effective, but that they were equally effective, in delaying or preventing diabetes in women with impaired glucose tolerance and a history of GDM. Both reduced the risk by about 50% at 3 years. This was striking because in parous women without GDM, the reductions were 49% and 14%, respectively. Metformin thus appeared to be more effective in women with a history of GDM.
The effects of the interventions persisted over a 10-year follow up of the DPP population. In women with a history of GDM, the intensive lifestyle intervention and metformin reduced progression to diabetes by 35% and 40%, respectively, over 10 years (J Clin Endocrinol Metab. 2015 Apr;100[4]:1646-53).
Pregnancy presents a stress test for beta cell function, and gestational diabetes clearly is a harbinger of further deterioration in beta-cell function and metabolic abnormalities in the mother. Because of these risks and because early intervention makes a difference, surveillance is critically important. Most women see their ob.gyn. as their primary care physician in the 10 years following a pregnancy – the time when more than 50% of all cases of subsequent diabetes will occur – and many continue to see their ob.gyns. in the longer term, as their risk continues to linger.
Immediately after a pregnancy with GDM, ob.gyns. can counsel women not only about their risks of developing type 2 diabetes and the importance of screening, but also about the beneficial impact of lifestyle modification, caloric restriction and weight loss if necessary, and increased exercise. Mothers should also know that GDM is a family affair, and that lifestyle changes that are beneficial for the mother will be equally beneficial for the baby.
The Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study taught us that there are continuous linear relationships between maternal glucose and adverse fetal outcomes like birth weight and percent body fat greater than the 90th percentile. Longitudinal studies of the Pima Indians showed us that offspring of women who had diabetes during pregnancy were more likely to be obese and more likely to develop diabetes than offspring of women who did not have diabetes during pregnancy. Even when GDM has been well treated and controlled, we should have heightened awareness to the potential risks in the fetus and the growing child and adolescent.
Patients who are found to have subsequent type 2 diabetes should know that aggressive therapy early on in the natural history of the disease reduces the risk of microvascular and macrovascular complications. And as the DPP has demonstrated, lifestyle interventions and metformin may also keep women who are found to have prediabetes outside of pregnancy from progressing on to diabetes.
Dr. Ratner is the chief scientific and medical officer for the American Diabetes Association. He reported having no financial disclosures relevant to this Master Class.