Early Screening for Gestational Diabetes

Risk-Based Screening Algorithm

Women with a BMI ≥30 kg/m² should undergo early glucose testing, as this is a strongly supported indication for early screening, according to the American College of Obstetricians and Gynecologists 1, 2, 3
A previous history of gestational diabetes carries a 4.14-fold increased risk, prompting early screening, as recommended by the American Diabetes Association 1
First-degree family history of diabetes is a risk factor for gestational diabetes, according to the American Academy of Family Physicians 6, 1
High-risk ethnicity, such as Hispanic, Native American, South or East Asian, African American, or Pacific Islander, is a risk factor for gestational diabetes, as noted by the American College of Obstetricians and Gynecologists 1
Previous macrosomic infant (>4.05 kg or 9 lb) is a risk factor for gestational diabetes, according to the American College of Obstetricians and Gynecologists 1
Polycystic ovary syndrome is a risk factor for gestational diabetes, as recommended by the American College of Obstetricians and Gynecologists 1
Glycosuria is a risk factor for gestational diabetes, according to the American Diabetes Association 4, 6

If the OGTT at 19 weeks is negative in a high-risk woman, mandatory repeat screening at 24-28 weeks is required, as recommended by the American College of Obstetricians and Gynecologists 4, 5, 1, 2, 3

The one-step approach (75g OGTT) involves fasting, 1-hour, and 2-hour glucose measurements, with diagnostic thresholds of Fasting ≥92 mg/dL, 1-hour ≥180 mg/dL, 2-hour ≥153 mg/dL, as recommended by the American Diabetes Association 5, 7, 8, 2
Any single abnormal value is diagnostic, according to the American Diabetes Association 5, 7, 8
The two-step approach involves an initial 50g glucose challenge test (non-fasting), followed by a 100g OGTT if ≥130-140 mg/dL at 1 hour, with diagnostic thresholds for 100g OGTT: Fasting ≥95 mg/dL, 1-hour ≥180 mg/dL, 2-hour ≥155 mg/dL, 3-hour ≥140 mg/dL, as recommended by the American College of Obstetricians and Gynecologists 5, 7, 8
At least two abnormal values are required for diagnosis, according to the American Diabetes Association 4, 5, 7, 8

For women without high-risk factors, the standard screening window remains 24-28 weeks gestation, as recommended by the U.S. Preventive Services Task Force 5, 7, 8, 2

Women meeting all of the following criteria may potentially skip screening entirely: age <25 years, BMI ≤25 kg/m², no history of abnormal glucose tolerance, no adverse obstetric outcomes, no first-degree relative with diabetes, and not from a high-risk ethnic group, as noted by the American Academy of Family Physicians 6, 3, 4

Not repeating screening at 24-28 weeks after negative early testing in high-risk women, as recommended by the American College of Obstetricians and Gynecologists 1, 2
Performing early screening in average-risk women without clinical indication, which lacks evidence support, according to the U.S. Preventive Services Task Force 2
Using early screening results to exclude the need for standard 24-28 week testing, as gestational diabetes develops progressively throughout pregnancy, as noted by the American Diabetes Association 4, 5