Screening for Gestational Diabetes

Standard Screening Time

The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women be screened for gestational diabetes between 24-28 weeks of gestation, which is the optimal period for detecting gestational diabetes (GDM) 1, 2, 3
This timing is based on the Hyperglycemia and Adverse Pregnancy Outcomes (HAPO) study, which demonstrated that the risk of adverse maternal, fetal, and neonatal outcomes increases continuously with increasing maternal glucose levels at 24-28 weeks 1

Women with high-risk factors should be screened at the first prenatal visit (12-14 weeks) and, if negative, repeat screening at 24-28 weeks 4, 5
High-risk factors include a body mass index (BMI) ≥30 kg/m², previous history of GDM, family history of diabetes, belonging to high-risk ethnic groups, previous history of macrosomia, polycystic ovary syndrome, and glucosuria 4, 5

The American Diabetes Association (ADA) recommends a one-step approach using a 75g oral glucose tolerance test (OGTT) with plasma glucose measurement at fasting, 1 hour, and 2 hours 1
Diagnosis of GDM is made if any of the following values are met or exceeded: fasting ≥92 mg/dL, 1 hour ≥180 mg/dL, or 2 hours ≥153 mg/dL 1, 3
The two-step approach, supported by ACOG, involves a 50g glucose challenge test (GCT) followed by a 100g OGTT if the GCT is abnormal 1, 6

If gestational diabetes is diagnosed, immediate management includes lifestyle therapy, and 80-90% of women with mild GDM can be managed with lifestyle therapy alone 1, 2
Treatment reduces the risk of large-for-gestational-age babies and preeclampsia 1
All women with GDM should undergo postpartum evaluation 4-12 weeks after delivery with a 75g OGTT using non-pregnant criteria 4
Lifetime screening for prediabetes and type 2 diabetes is recommended at least every 3 years 1, 2, 4

Not repeating screening at 24-28 weeks in high-risk women with an initial negative test can result in delayed diagnosis 4
Not performing a diagnostic OGTT after a positive glucose challenge test can lead to missed diagnoses 6
Using different thresholds without considering the population's risk profile can lead to under or over-diagnosis 6
Not providing postpartum follow-up misses the critical opportunity for type 2 diabetes prevention 4