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Gestational Diabetes Mellitus (GDM)

Diabetes during pregnancy

Every year, one in 10 expectant mothers develop so-called gestational diabetes, a type of diabetes that appears specifically during pregnancy. Though the condition usually resolves once the baby is born, women who develop gestational diabetes are at increased risk of developing the disease again during future pregnancies — and as many as 50 percent of these women will develop type 2 diabetes in the decade after they give birth.

Who's at risk?

Women are at risk for gestational diabetes if they:

  • Previously delivered a larger-than-average baby

  • Are overweight or obese

  • Have a strong family history of diabetes

Most women with gestational diabetes will not notice any symptoms, as the classic signs — thirstiness, frequent trips to the bathroom — can be considered normal during pregnancy. For that reason, the condition is usually diagnosed with a blood test.

How is it diagnosed?

The condition is most often diagnosed between 24 and 28 weeks of pregnancy with a laboratory test that doctors call the oral glucose tolerance test. Women at high risk for gestational diabetes will be tested at their first prenatal appointment.

  • The test is usually performed in the morning, when the patient has avoided food for at least eight hours.

  • Patients are asked to consume a sweet drink that contains 75 grams of glucose.

  • The patient’s blood glucose is tested before drinking the juice, then one and two hours after drinking the juice.

  • Gestational diabetes is diagnosed if blood glucose levels are above 92 before drinking the juice, above 180 an hour after drinking the juice or above 153 two hours after drinking the juice.

How is gestational diabetes treated?

Keeping blood glucose levels under control will help ensure the health of mother and baby. Doctors will generally help patients make the following lifestyle changes:

  • Switch to a low-carb diet, under the guidance of a nutritionist.

  • Reduce the number of calories consumed per day (for women who are overweight or obese).

  • Follow a light daily exercise routine.

If diet and exercise aren’t enough, the doctor might prescribe insulin.Pregnant women should try to keep their blood glucose within the following ranges:


Time of DayHealthy Range of Blood Glucose
Fasting (upon waking)60-90 (or 95) mg/dl
Before a Meal60-100 mg/dl
One Hour After a Meal<140 mg/dl
Adapted from: ACOG Committee on Practice Bulletins. ACOG Practice Bulletin. Clinical management guidelines for obsretrician-gynecologists. Number 60, March 2005. Pregestationsl diabetes mellitus. Obstet Gynecol, 2005; Vol. 105(3): pp. 675-85. Reproduced with permission of Lippincott Williams & Wilkins.

What to expect after delivery

Gestational diabetes typically disappears after the baby is born. Women should be carefully monitored by their doctors and retested for diabetes at six to 12 weeks postpartum. Once blood glucose control returns to normal, women should be screened for diabetes every three years because of the increased risk of developing type 2 diabetes in the years that follow delivery.

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