Oral Glucose Tolerance Test (OGTT) in Pregnancy

When is the OGTT done?

The Oral Glucose Tolerance Test (OGTT) is usually performed between 24 and 28 weeks of pregnancy, when insulin resistance is highest. If certain risk factors are present, it may be advised earlier.

Why are women advised to undergo an OGTT?

All pregnant women are at risk of developing gestational diabetes, even if they had no diabetes before pregnancy. Routine screening helps detect and manage it early.

Gestational diabetes can lead to:

Baby growing larger than normal
Increased risk of delivery complications
Health problems for the mother

Most cases can be managed with diet and exercise, though some may require insulin. Blood sugar usually returns to normal after delivery, but follow-up testing is important.

Before the Test

Follow a normal, unrestricted diet for three days before the test.
Fasting for 8–10 hours (water only) before the test.

How the Test is Done

Fasting blood sample is taken.
Drink a solution containing 75 grams of glucose in 200 ml water.
Blood samples taken 1 hour and 2 hours after the drink.
Remain seated and avoid physical activity during the test.
Test duration: approximately 2–3 hours.

Interpretation of Results (IADPSG)

Time of Test	Normal Value
Fasting	≤ 92 mg/dL (≤ 5.3 mmol/L)
1 hour after glucose	≤ 180 mg/dL (≤ 10.0 mmol/L)
2 hours after glucose	≤ 153 mg/dL (≤ 8.6 mmol/L)

➡️ One abnormal value is sufficient to diagnose gestational diabetes.

Other Tests That Can Diagnose Diabetes

HbA1c ≥ 6.5%
Fasting plasma glucose ≥ 126 mg/dL (7.0 mmol/L)
Random plasma glucose ≥ 200 mg/dL (11.1 mmol/L)

Mathi Hospitals

Oral Glucose Tolerance Test