Onset of T2DM after gestational diabetes: What the prevention paradox tells us about risk.

This study investigates the effect of severity of gestational diabetes (GDM) on likelihood of post-delivery glucose testing and early onset Type 2 diabetes (T2DM). We asked if clinical focus on relative risk (RR), i.e. greater probability of T2DM onset in a higher-severity group, contributes to missed opportunities for prevention among women with lower-severity GDM. A sample of 12,622 continuously-insured women with GDM (2006-2015) was drawn from a large national dataset (OptumLabs® Data Warehouse) and followed for 3-years post-delivery. Higher-severity GDM was defined as addition of hypoglycemic therapy to standard of care for GDM. We found that women with higher-severity (n = 2627) were twice as likely as lower-severity women (n = 9995) to obtain glucose testing post-delivery. Moreover, 357 (13.6%) of the higher-severity women developed T2DM by year-3 vs. 600 (6.0%) lower-severity women. In an analysis of the population attributable fraction (PAF), defined as the contribution of excess risk to population prevalence, lower-severity women contributed more cases to diabetes rates than higher-risk women (PAF 79% vs. 21%), despite an increased RR in the higher-severity group (13.6% vs. 6.0%, RR 2.26, 95%CI 2.00, 2.56). Projecting out to the 327,950 U.S. deliveries in 2014, we estimate that 9277 higher-severity women (13.6%) and 15,584 lower-severity women (6.0%), will have developed T2DM by 2018. These data demonstrate that lower-severity GDM contributes substantially to the diabetes epidemic. Greater awareness of clinical and cost implications of gaps in follow-up for lower-severity GDM may strengthen the likelihood of post-delivery testing and primary care referral, and thus reinforce the path to prevention.