Reference values for 75 g oral glucose tolerance test in pregnancy

Area of Science:

• Obstetrics and Gynecology
• Endocrinology
• Clinical Chemistry

Background:

• Glucose metabolism changes significantly during pregnancy.
• Establishing normal reference ranges for glucose tolerance tests is crucial for accurate diagnosis of gestational diabetes.
• Existing reference ranges may not adequately account for gestational stage.

Purpose of the Study:

• To establish normal reference values for the 75 g oral glucose tolerance test (OGTT) in pregnancy.
• To determine if reference values differ between the second and third trimesters.
• To propose updated upper limits for interpreting OGTT results based on gestational age.

Main Methods:

• A 75 g oral glucose tolerance test was administered to 212 pregnant women without predisposing factors for glucose intolerance.
• Participants were grouped by gestational period: mid-pregnancy (14-20 weeks) and late pregnancy (28-37 weeks).
• Statistical analysis was performed to compare glucose levels between the two gestational groups.

Main Results:

• Statistically significant differences were observed in glucose levels one and two hours post-load between the mid-pregnancy and late-pregnancy groups.
• The 97.5th percentile (upper limit of normal) for the two-hour glucose level was 7.5 mmol/l in the second trimester.
• The 97.5th percentile for the two-hour glucose level was 9.6 mmol/l in the third trimester.

Conclusions:

• Reference ranges for the oral glucose tolerance test in pregnancy must consider the period of gestation.
• Updated, gestational age-specific upper limits for the 75 g OGTT are proposed.
• These findings support more accurate interpretation of glucose tolerance tests during pregnancy.