LOWERING THE THRESHOLD FOR THE DIAGNOSIS OF GESTATIONAL DIABETES

OBJECTIVE: Our purpose was to determine whether lowering the diagnosti c threshold for gestational diabetes mellitus on 3-hour 100 gm oral gl ucose tolerance testing will select a population at risk for adverse p erinatal outcome. STUDY DESIGN: In this retrospective study 434 patien ts with an abnormal 50 gm glucose screen result (greater than or equal to 140 mg/dl) underwent a standardized 3-hour oral glucose tolerance test. The results were stratified according to maternal weight and the criteria recommended by Sacks or Carpenter. Birth weight and rate of macrosomia were the primary perinatal outcome variables analyzed. RESU LTS: Analysis of the data set stratified according to the Sacks criter ia revealed results very similar to the Carpenter criteria data set. P atients who would have been newly diagnosed with gestational diabetes mellitus only if the lowered criteria were used (group 2) were older a nd heavier No other variable comparisons achieved statistical signific ance. When the same patients were stratified according to prepregnancy weight, overweight patients were older, gained less weight during the third trimester, underwent cesarean section more often, and had highe r cumulative maternal morbidity. Regression analysis showed that the d egree of hyperglycemia did not predict macrosomia or influence birth w eight, but prepregnant maternal body mass index was associated with ma crosomia. CONCLUSIONS: Fetal macrosomia is influenced by maternal prep regnant body mass index. Lowering the glucose tolerance test threshold would result in overdiagnosis of gestational diabetes mellitus withou t improving perinatal outcome.