Gestational diabetes - Is a 50-g screening result >= 200 mg/dL diagnostic?

OBJECTIVE: To evaluate the diagnosis of gestational diabetes based on a 50- g, one-hour glucose screening test result greater than or equal to 200 mg/d L. STUDY DESIGN: Retrospective ascertainment of pregnant women who had a 50-g, one-hour glucose screening test result greater than or equal to 200 mg/dL was performed among prenatal care registrants. The diagnosis of gestational diabetes was determined by 100-g, three-hour oval glucose tolerance test ( GTT) results and/or repeated fasting serum glucose measures. RESULTS: In 1995, 69 women were referred to the gestational diabetes clinic with a 50-g result greater than or equal to 200 mg/dL. Four women could no t be classified, two had pregestational glucose intolerance and four charts were unavailable. Of the remaining 59 women, 11 (19%) had normal three-hou r GTTs, and 48 (81%) were diagnosed with gestational diabetes (35 [59%], A( 1); 13 [22 %], A(2)). There was one large-for-gestational-age (LGA) infant born in the nondiabetic group (9%), 13 LGA infants born in the A(1) group ( 37%) and 6 LGA infants born to the A(2) diabetics (46%). The relationship b etween maternal diagnosis and LGA outcome was statistically significant. CONCLUSION A 50-g screening test result greater than or equal to 200 mg/dL is not diagnostic of gestational diabetes. Nearly one of five such women ha d a normal three-hour oral GTT Overdiagnosis of gestational diabetes may le ad to unnecessary pregnancy surveillance and intervention.