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Reviewed by the Faculty of Harvard Medical School

Gestational Diabetes

What Is It?

Gestational diabetes is the appearance of higher-than-expected blood sugars during pregnancy. Once it occurs, it lasts throughout the remainder of the pregnancy. It affects up to 14% of all pregnant women in the United States. It is more common in African-American, Latino, Native American and Asian women than in Caucasians. Like the other types of diabetes, gestational diabetes results when sugar (glucose) in the bloodstream can't be moved efficiently into body cells, such as muscle cells, that normally use sugar as a body fuel. The hormone insulin helps to move sugar from the bloodstream into the cells. In gestational diabetes, the body does not respond well to insulin, unless insulin can be produced or provided in larger amounts. In most women, the disorder goes away when the pregnancy ends, but women who have had gestational diabetes are at increased risk of developing type 2 diabetes later.

Diabetes occurs during pregnancy because hormones produced in a pregnancy make the body resistant to insulin's effects. These hormones include growth hormone and human placental lactogen. Both of these hormones are essential to a healthy pregnancy and fetus, but they partially block the action of insulin. In most women, the pancreas reacts to this situation by producing enough additional insulin to overcome the insulin resistance. In women with gestational diabetes, not enough extra insulin is produced, so sugar accumulates in the bloodstream.

As the fetus grows larger, more hormones are produced. Because it is the time when these hormone levels are highest, gestational diabetes usually starts in the last trimester of pregnancy. After delivery, the body's hormones quickly return to nonpregnant levels. Typically, the amount of insulin that is made by the pancreas is adequate for your needs once again, and blood glucose levels return to normal.

Symptoms

Some pregnant women with gestational diabetes have the symptoms of diabetes that are associated with high blood glucose (hyperglycemia). These include:
  • Increased thirst
  • More frequent urination
  • Weight loss despite increased appetite
  • Fatigue
  • Nausea or vomiting
  • Yeast infections
  • Blurred vision

However, some women have no recognizable symptoms. This is why screening tests for this disease are recommended for all pregnant women.

Diagnosis

Gestational diabetes usually is diagnosed during the routine testing that occurs as a part of complete prenatal care. In a normal pregnancy, blood sugars are about 20% lower than is seen in women who aren't pregnant because the developing fetus absorbs some glucose from the mother's blood. Diabetes is evident if blood sugar levels are higher than expected for pregnancy. To find gestational diabetes in its earliest form, doctors usually give the pregnant woman a heavily sugared drink prior to testing the blood so that the body's sugar-processing capability is maximally challenged. This is known as an oral glucose tolerance test.

It is appropriate for a woman who is overweight, has a family history of diabetes, or has symptoms suggesting diabetes to undergo testing at the first prenatal visit. All other women should be tested after 24 weeks of gestation. Most often, the testing is done between 24 and 28 weeks.

Expected Duration

Diabetes that appears during a pregnancy usually goes away after the pregnancy is over. However, the fact that your pancreas can't keep up with insulin demands during pregnancy shows that it is operating without much reserve even when you are not pregnant. Women who have gestational diabetes are at increased risk of developing type 2 diabetes later in life. Twenty percent of women with gestational diabetes have elevated blood sugar levels that continue for a few weeks after they give birth. These women are the most likely to develop type 2 diabetes later in life.

Prevention

Gestational diabetes usually cannot be prevented. However, careful control of your weight before pregnancy may reduce your risk. Very low-calorie diets are not recommended during pregnancy because adequate nutrition is important.

Complications of gestational diabetes can be prevented by carefully controlling your blood sugar and by being monitored by an obstetrician throughout your pregnancy.

After your pregnancy, you can reduce your risk of developing type 2 diabetes. Regular exercise and a reduced-calorie diet have been shown to lower the risk of diabetes in people who are at high risk for diabetes. The medicine metformin (Glucophage) can help to prevent diabetes in people who have mildly elevated blood glucose levels outside of pregnancy, but who do not have levels high enough for a diagnosis of diabetes.

Treatment

Some pregnant women are able to keep blood glucose at healthy levels by managing their diet. This requires consultation with a dietitian to set up a diet plan, and regular monitoring of blood glucose.

If diet does not control blood glucose adequately, your doctor will prescribe insulin. The oral medicines metformin (Glucophage), glyburide and acarbose are also occasionally used. Insulin has been used during pregnancy to treat many women with type 1 and gestational diabetes and is safe for the fetus when blood sugar is monitored closely.

Gestational diabetes creates dangers for the developing fetus. Unlike type 1 diabetes, gestational diabetes rarely causes serious birth defects. However, in gestational diabetes the baby can have complications during delivery because it may be larger than normal (a large body size for a baby is called macrosomia). Large baby body size comes from the extra sugar exposure. If the diabetes is not treated carefully, high blood sugar levels can increase the chance of fetal death prior to delivery (stillbirth). Delivery itself may be more difficult, and the need for Caesarean delivery is more frequent. If natural labor and delivery has not occurred by 38 weeks of pregnancy, your doctor probably may recommend inducing labor or delivering by surgery to avoid macrosomia.

Complications also can affect the baby right after birth. Prior to delivery, the fetus's pancreas gets used to making a large amount of of insulin each day, to help manage the fetus's exposure to high blood sugar levels. After delivery, it takes time for the baby's pancreas to adjust. If the baby makes too much insulin during its first hours after birth, low blood sugar may occur temporarily. If you have gestational diabetes, your baby's blood sugar should be measured after birth. If necessary, intravenous glucose will be given to the baby. Other chemical imbalances also may occur temporarily, so the baby's calcium and blood count also should be monitored.

When To Call A Professional

All pregnant women should receive prenatal care and have regular visits with a qualified doctor or midwife. Most women should receive an oral glucose challenge test during weeks 24 to 28 of their pregnancies. Women at high risk of diabetes should get tested earlier.

Prognosis

Most of the time, gestational diabetes is a short-term condition. In more than three-quarters of women who develop gestational diabetes, blood glucose levels go back to normal once the pregnancy ends. However, the pancreas has shown that it is operating without much reserve. Women who have had gestational diabetes are at increased risk of developing it again in subsequent pregnancies. They are also at increased risk of developing type 2 diabetes later in life and should have their blood glucose checked regularly even after the pregnancy is over.

Additional Info

National Institute of Child Health & Human Development
Building 31, Room 2A32
MSC 2425
31 Center Drive
Bethesda, MD 20892-2425
Toll-Free: 1-800-370-2943
Fax: 1-301-496-7101
Website: www.nichd.nih.gov

Last updated February 11, 2014




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