Gestational Diabetes


What Is It?

Gestational diabetes is the appearance of diabetes during pregnancy. Once it occurs, it lasts throughout the remainder of the pregnancy. It affects approximately 7 percent of all pregnant women. 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 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 certain hormones produced in a pregnancy make the body resistant to insulin’s effects. These hormones include cortisol and human placental lactogen. Both of these hormones are essential to a healthy pregnancy and fetus, but each partially blocks 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, and sugar can’t be processed correctly by the body, so sugar accumulates in the bloodstream.

As the fetus grows larger, larger quantities of the hormones that interfere with insulin are produced. For this reason, gestational diabetes usually starts in the last trimester of pregnancy. At delivery, the body’s hormones quickly return to nonpregnant levels. Typically, the pancreas is able to produce enough insulin once again, and blood-glucose levels return to normal.


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 and blurred vision. However, some women have no recognizable symptoms, which is why screening tests for this disease are recommended for almost all pregnant women.


Gestational diabetes most often is diagnosed during the routine testing that occurs as a part of complete prenatal care. Diabetes is evident if blood sugar levels are high. In order 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. Most other women should be tested 24 to 28 weeks into their pregnancy.

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 suggests that it is operating without much reserve even when you are not pregnant. It is well demonstrated that women who have gestational diabetes are at increased risk of developing type 2 diabetes later in life.


Gestational diabetes usually cannot be prevented. However, women who are overweight during pregnancy have a higher risk of the disease, and 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.


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. Oral medicines to lower blood sugar are not approved by the U.S. Food and Drug Administration for use in pregnant women because of possible adverse effects on the fetus. However, insulin has been used during pregnancy to treat many women with type 1 and gestational diabetes and appears to pose no risk to the fetus when blood sugar is monitored closely.

Gestational diabetes can pose some risks and potential problems to the developing fetus. Unlike type 1 diabetes, it rarely causes serious birth defects because most cases do not occur until the last trimester of pregnancy. However, a fetus that has developed normally can have complications during delivery because the fetus can be larger than normal (called macrosomia) as a result of its exposure to excessive glucose. Poorly managed blood-sugar levels may increase the chance of fetal death prior to delivery. 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 will advise inducing labor or delivering by surgery to avoid macrosomia.

Complications also can affect the baby right after birth. Prior to delivery, the fetus makes abundant amounts of insulin when it is exposed to the mother’s high blood-sugar levels. After delivery, before the baby’s own insulin production adjusts, 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, 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 physician or midwife. Most women should receive an oral glucose-challenge test during weeks 24 to 28 of their pregnancies, and women at high risk of diabetes should get tested earlier.


Most of the time, gestational diabetes is self-limiting. 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 sent out a signal that it might not always be able to produce as much insulin as the body needs. 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. Some experts advise that people at high risk of diabetes have their blood glucose tested every two years.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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