A rationale for omitting two-hour postprandial glucose determinations in gestational diabetes

Objective: In making decisions regarding initiation of insulin therapy in gestational diabetes, most maternal-fetal obstetricians rely more on elevated fasting glucose values than on elevated 2-hour postprandial levels. We sought to determine whether the latter test is necessary. Study Design: From the patients with gestational diabetes mellitus managed over a 17-month period at Grady Memorial Hospital, we retrospectively analyzed data to determine whether normal (< 105 mg/dl) fasting plasma glucose values predict elevated 2-hour postprandial values and whether the latter predict adverse outcome. Results: From 194 patients with gestational diabetes mellitus, 546 paired fasting and 2-hour postprandial glucose values were recorded. Fasting levels were normal in 467 (85%); in those, 2-hour levels were < 120 mg/dl in 83% and < 140 in fully 96%. In 131 women with all fasting plasma glucose values normal, the birth weights and the rates of cesarean delivery, shoulder dystocia, and macrosomia were similar, regardless of whether 2-hour postprandial glucose values were>120. The actual cost of the 546 2-hour postprandial glucose tests was nearly $10,000. Conclusion: For metabolic surveillance in gestational diabetes mellitus, the 2-hour postprandial glucose test seems unnecessary, provided fasting plasma glucose values remain normal.