Screening and diagnosing gestational diabetes mellitus (GDM)

At 24-28 weeks gestation
Administer 50-g oral glucose load
Check serum glucose 1 hr later
If blood glucose less than 140 mg/dL → GDM unlikely; no further testing
If blood glucose greater than 140 mg/dL:
Check fasting serum glucose
Administer 100-g oral glucose load
Check serum glucose each hour afterward for 3 hr
Diagnosis of GDM (at least 2 abnormal values, National Diabetes Data Group criteria):
Fasting: at least 105 mg/dL
1 hr: at least 190 mg/dL
2 hr: at least 165 mg/dL
3 hr: at least 145 mg/dL