Gestational Diabetes Mellitus: Why the Controversy?

Abstract

Gestational diabetes mellitus (GDM)6 has been defined as “any degree of glucose intolerance with onset or first recognition during pregnancy.” With the dramatic rise in the prevalence of type 2 diabetes, some organizations have advocated that hyperglycemia first detected in pregnancy should be classified as either diabetes mellitus in pregnancy or GDM. The rationale for identifying GDM is that it results in complications for both the fetus (e.g., large baby, neonatal hypoglycemia) and mother (e.g., preeclampsia, increased risk of cesarean delivery, and markedly increased likelihood of subsequent type 2 diabetes). Treatment of GDM reduces some of the adverse outcomes. Despite the 5 international workshops devoted to GDM since 1979, there is considerable controversy surrounding identification of GDM. Both the screening and diagnostic criteria vary among countries and commonly between obstetric and diabetes organizations in a single country. Recommendations for screening encompass “do not screen,” selective screening (high risk only), and universal. Moreover, the screening techniques vary; fasting glucose, random glucose, and oral glucose challenge are all used. The criteria for diagnosis are even more controversial. The major items of contention are the number of steps (1 or 2), the glucose load (75 g or 100 g), the duration of the test (2 h or 3 h), the glucose cutoff values, and whether 1 or 2 high glucose values are required. The Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study was designed to determine the relationship between maternal blood glucose concentrations and adverse pregnancy outcomes. The prospective, randomized, multinational study included 23316 women who had a 75-g oral glucose tolerance test (OGTT) at 24–32 weeks of gestation. The study showed that the risk of adverse events increased continuously as a function of maternal glycemia. No convenient thresholds for increased risk were observed, and each of the 3 values (fasting, 1 h, …