Medicalising pregnancy with new diagnostic criteria for gestational diabetes mellitus: do we need more evidence?

Unifying the diagnosis of gestational diabetes mellitus: Introducing the NPRP criteria

AIMS

Disagreement about the appropriate criteria for the diagnosis of gestational diabetes mellitus (GDM) persists. This study examines an alternative approach which combines information from all time-points on the glucose tolerance test (GTT) into a single index and expands the GDM spectrum into four categories using data from three geographically and ethnically distinct populations.

METHODS

A retrospective observational study design was used. Data from Wisconsin, USA (723 women) was used in derivation of the criterion and data from Doha, Qatar (1284 women) and Cape Town, South Africa (220 women) for confirmation. Pregnant women without pre-existing diabetes with a GTT done between 23 and 30 weeks gestation were included. A novel index was derived from the GTT termed the weighted average glucose (wAG). This was categorized into four pre-defined groups (henceforth National Priorities Research Program (NPRP) criterion); i) normal gestational glycemia (NGG), ii) impaired gestational glycemia (IGG), iii) GDM and iv) high risk GDM (hGDM).

RESULTS

In the Doha cohort, compared to the NGG group, the odds of large for gestational age babies increased 1.33 fold (P = 0.432), 2.86 fold (P < 0.001) and 3.35 fold (P < 0.001) in the IGG, GDM and hGDM groups respectively. The odds of pregnancy induced hypertension increased 2.10 fold (P = 0.024) in GDM & hGDM groups compared to the IGG and NGG groups. In the Cape Town cohort, a third of women in the GDM group and two-thirds in the hGDM group progressed to T2DM at 5 years.

CONCLUSIONS

The NPRP categorization identifies four distinct risk clusters of glycemia in pregnancy which may aid better decision making in routine management, avoid potential over-diagnosis of women at lower risk of complications and assist with diabetes prevention in women at high-risk after an index pregnancy with GDM.

Gestational diabetes: opportunities for improving maternal and child health

Gestational diabetes, the most common medical disorder in pregnancy, is defined as glucose intolerance resulting in hyperglycaemia that begins or is first diagnosed in pregnancy. Gestational diabetes is associated with increased pregnancy complications and long-term metabolic risks for the woman and the offspring. However, the current diagnostic and management strategies recommended by national and international guidelines are mainly focused on short-term risks during pregnancy and delivery, except the Carpenter-Coustan criteria, which were based on the risk of future incidence of type 2 diabetes post-gestational diabetes. In this Personal View, first, we summarise the evidence for long-term risk in women with gestational diabetes and their offspring. Second, we suggest that a shift is needed in the thinking about gestational diabetes; moving from the perception of a short-term condition that confers increased risks of large babies to a potentially modifiable long-term condition that contributes to the growing burden of childhood obesity and cardiometabolic disorders in women and the future generation. Third, we propose how the current clinical practice might be improved. Finally, we outline and justify priorities for future research.