It was not that many years ago that there was an active debate about whether gestational diabetes mellitus (GDM) was an actual disease that warranted treatment. Oh how the pendulum has swung! With the results of 2 well-conducted large multicenter randomized clinical trials both of which show maternal and neonatal benefits of treatment, few physicians now would undertake this argument. Additionally, the results of the HAPO Study (hyperglycemia and adverse pregnancy outcomes) suggest increased adverse pregnancy outcome with maternal glucose levels below our current diagnostic thresholds for GDM. The positive results of these studies combined with the “perfect storm” of the current obesity epidemic (adult and childhood) has inspired both US and international diabetes mellitus experts to propose expansion of the diagnostic criteria for GDM that would increase the incidence from 4-7% up to 16%.
Given the current scientific data, I would argue vigorously against such a profound paradigm shift for the following reasons:
The HAPO Study was an observational study, not a treatment trial. Although there is an association between a lower level of glycemia and adverse outcome, there is insufficient evidence to determine whether nutritional modification would have a clinically significant impact at this glycemic level. Randomized clinical trials of lifestyle modifications for overweight and obese women without diabetes mellitus have not improved perinatal outcomes consistently.
Although it could be argued that nutritional modification itself poses little risk of harm to mother and fetus, there is still the potential for increased harm because of the designation of a woman as having GDM (and thus being labeled as a “high-risk” pregnancy). A diagnosis of GDM increases the overall utilization of healthcare services by creating additional prenatal visits and increased discomforts, inconvenience, and costs that are associated with daily blood glucose monitoring. Additionally, women with a diagnosis of GDM are more likely to have additional ultrasound scans for fetal growth assessment, are more likely to have labor induction, and may be more likely to have cesarean delivery because of over use of these tests and potentially unnecessary therapies.
In summary, a change in the diagnostic criteria for GDM and the resulting massive expansion of treatment can be justified only after level I evidence has been obtained that regards treatment benefit, potential harms, and costs. Well-conducted interventional trials (rather than expert opinion and biologic plausibility) should drive the creation of new GDM screening and treatment guidelines.