Gestational diabetes mellitus requires five core tests: fasting blood glucose, oral glucose tolerance test, glycated hemoglobin, urine glucose and urine ketone bodies, and fetal ultrasound.
- Fasting Blood Glucose
Fasting blood glucose is a basic indicator for diagnosing gestational diabetes mellitus. Venous blood sampling is performed after 8 hours of fasting.The normal value should be below 5.1 mmol/L. Abnormal results require comprehensive evaluation with other tests.This test reflects basal insulin secretion function. The first screening is recommended at 24–28 weeks of gestation. - Oral Glucose Tolerance Test (OGTT)
The oral glucose tolerance test is the gold standard for diagnosing gestational diabetes mellitus.After fasting, 75 g of glucose is taken orally, and blood glucose is measured at 1 hour and 2 hours.
The three threshold values are: Fasting: 5.1 mmol/L
1 hour: 10.0 mmol/L
2 hours: 8.5 mmol/L
A diagnosis can be made if any one value exceeds the threshold.This test assesses the body’s ability to regulate glucose load.
- Glycated Hemoglobin (HbA1c)
Glycated hemoglobin reflects the average blood glucose level over the past 8–12 weeks.The normal value should be below 6%.
During pregnancy, the shortened red blood cell lifespan may underestimate actual blood glucose, so it is not used as an independent diagnostic criterion, but can evaluate long-term glycemic control.Rechecking is recommended every 2–3 months. - Urine Glucose and Urine Ketone Bodies
Urine glucose testing is simple but has low specificity; positive results must be interpreted with blood glucose levels.Positive urine ketones may indicate severe insulin deficiency or insufficient energy intake, requiring vigilance for the risk of diabetic ketoacidosis.
Both tests use morning urine samples and are suitable for daily monitoring. - Fetal Ultrasound
Fetal ultrasound mainly evaluates amniotic fluid index, fetal abdominal circumference, and weight gain.Examinations are required every 2–4 weeks in late pregnancy.Macrosomia or polyhydramnios suggests poor blood glucose control.
Ultrasound can also screen for congenital malformations; a detailed structural scan is recommended at 18–22 weeks of gestation.
In addition, doctors may perform other relevant tests based on individual conditions, such as liver and kidney function, blood lipids, thyroid function, and autoantibody tests.
It should be noted that each pregnant woman’s condition is different, and specific test items and frequency may vary.Before testing, follow your doctor’s advice for preparation, and truthfully inform your doctor of your medical history and symptoms during the examination.
If diagnosed with gestational diabetes mellitus, actively cooperate with your doctor’s treatment and management, including diet control, exercise therapy, and blood glucose monitoring, to ensure the health of yourself and your fetus.Regular prenatal examinations are also very important to detect and manage any potential problems in a timely manner.