Undiagnosed asymptomatic hypoglycemia: Diet, insulin, and glyburide for gestational diabetic pregnancy

OBJECTIVE: The role of maternal hypoglycemia during pregnancy has not yet been established. We sought to estimate the prevalence of undiagnosed, asymptomatic hypoglycemic events that occur in diabetic patients. METHODS: All patients were evaluated using a continuous glucose monitoring system for 72 consecutive hours. The continuous glucose monitoring system measures in subcutaneous tissue interstitial glucose levels within a range of 40-400 mg/dL every 5 minutes for a total of 288 measurements per day. All patients were instructed regarding diabetic diet and assigned to pharmacological treatment as needed. Patients documented the time of food intake, insulin or glyburide administration, and all clinical hypoglycemic events. An asymptomatic hypoglycemic episode was defined as more than 30 consecutive minutes of glucose value below 50 mg/dL detected only by continuous glucose monitoring system reading without patient awareness. RESULTS: An evaluation of 82 patients with gestational diabetes was performed; 30 were insulin-treated, 27 were managed by diet only, and 25 were patients treated with glyburide. For purposes of comparison, data were obtained from 35 nondiabetic gravid women. Asymptomatic hypoglycemic events were identified in 19 of 30 (63%) insulin-treated patients and in 7 of 25 (28%) glyburide-treated patients. No hypoglycemic events were identified in patients with gestational diabetes mellitus treated by diet alone or in nondiabetic subjects. The mean recorded hypoglycemic episodes per day was significantly higher in insulin-treated patients (4.2 ± 2.1) than in glyburide-treated patients (2.1 ± 1.1), P = .03. In insulin-treated patients, the majority of the hypoglycemic events were nocturnal (84%), whereas in glyburide-treated patients, episodes were identified equally by day and night. CONCLUSION: Our data suggest that asymptomatic hypoglycemic events are common during pharmacological treatment in gestational diabetic pregnancies. We speculate that this finding may be explained by treatment modality rather than by the disease itself.