Newly proposed GDM screening protocol: unanswered questions remain

Evolution of current practice

The basis for our current screening strategy derives from the pioneering work of O'Sullivan and Mahan who established thresholds for fasting, 1-hour, 2-hour, and 3-hour glucose values that predicted a 50% risk of future diabetes.³

Shockingly, the clinical value of GDM screening and management only recently has been established by randomized trials.^5,6 And while we expend ever-greater efforts toward managing glucose values during pregnancy, less effort and success has been realized in achieving universal postpartum screening and long-term prevention, the rationale behind O'Sullivan and Mahan's original work.⁷

There has always been debate surrounding the proper methods for screening for GDM. Indeed, it has taken multiple international conferences to derive the screening system we use today: a system of essentially universal screening with a 1-hour, 50-g glucose challenge test followed by a diagnostic 3-hour, 100-g GTT when patients fail the 1-hour screen. Once a woman has been diagnosed with GDM, as a field we have embraced very aggressive glucose monitoring and control while largely ignoring women whose testing is normal or borderline. However, the reality is that glucose tolerance in pregnancy is a continuum and GDM is not a discrete disease. Indeed, one abnormal value on a 3-hour GTT is associated with adverse pregnancy outcomes.⁸