Gestational Diabetes

About 4 percent of pregnant women who have not previously been diagnosed with diabetes develop gestational diabetes, a form of diabetes that occurs only during pregnancy. It usually occurs during the fifth or sixth month of pregnancy.

In gestational diabetes, a pregnant woman’s blood sugar is high. If untreated, the high blood sugar can cause problems in her body and problems for her baby. Because it occurs after a baby’s organ systems have formed, gestational diabetes does not cause the birth defects sometimes seen in babies of mothers who had diabetes before becoming pregnant.

Gestational diabetes occurs more frequently in women who had gestational diabetes with an earlier pregnancy; in women who are African American, Hispanic/Latino American or American Indian; in obese women; and in women with a family history of diabetes. Women who fall into any of these groups should be screened at their first prenatal visit.

Causes

The exact cause of gestational diabetes is unknown. During the normal course of pregnancy, the placenta produces hormones that help the baby develop. Gestational diabetes occurs when those hormones block the action of the mother's insulin in her body, a condition called insulin resistance. As a result, the amount of glucose in the mother’s blood rises. In addition to causing problems for the mother’s body, the blood glucose passes through the placenta, causing high blood glucose levels in the baby. In response to this high glucose, the baby's pancreas makes extra insulin. Fetuses exposed to their mother’s high blood sugar grow more rapidly than normal. At birth, they are larger than normal, have higher body fat than normal and their internal organs are larger than normal, a condition called macrosomia. Immediately after birth, these babies might develop very a low blood glucose levels because they have a high level of insulin but are no longer exposed to high glucose from their mothers' blood. These babies are also at higher risk for breathing problems. Babies with excess insulin face a heightened risk of obesity and diabetes in late adolescence and adulthood. They may also face an increased risk of some cancers.

Gestational diabetes can usually be detected after the 20th week of pregnancy and usually disappears after pregnancy. Treatment includes dietary changes, physical activity and, if needed, medications.

Five to 10 percent of women with gestational diabetes develop diabetes (usually type 2 diabetes) when their pregnancy ends. Once you've had gestational diabetes, you have a two-in-three chance of it returning during future pregnancies. There is a 20 to 50 percent chance that women with gestational diabetes will develop type 2 diabetes within five to ten years of their pregnancy. Women who have had gestational diabetes can reduce their risk of developing type 2 diabetes by maintaining a healthy weight, getting regular physical exercise and eating a healthy diet.

For a few women, pregnancy actually reveals type 1 or type 2 diabetes they didn't know they had. Those women will require continued treatment.

Risk Factors

These are risk factors for developing gestational diabetes:

• Advancing age. Women older than 40 are more than twice as likely to develop it as women ages 25 to 29.

• History of diabetes in a first-degree relative. The risk is more than 1.5 times greater than in women without such a history. That risk grows to nearly double if your mother is the close relative with diabetes and nearly triple if both your parents have diabetes.

• Nonwhite ethnicity. The risk is 1.45 times greater for Hispanics, 1.75 times greater for African Americans and 2.32 times greater for Asians.

• High body mass index (BMI) before pregnancy. A BMI of 25 to 29.9 prior to pregnancy doubles the risk. The risk triples with a BMI of 30 or more. A 5-foot-6 woman weighing 154 pounds has a BMI of 25; the same woman weighing 186 pounds has a BMI of 30.

• Weight gain in early adulthood. A high BMI at age 18 followed by a weight gain of as little as 11 to 22 pounds by the time of pregnancy greatly increases the risk.

• Cigarette smoking.

• Previously bearing a child who weighed more than nine pounds.

• Previously having a stillbirth of unknown cause.

As part of your prenatal care, if you are at average risk, you should be screened for diabetes between your 24th and 28th weeks of pregnancy. If the blood-screening test indicates that you appear to have gestational diabetes, your doctor may seek to confirm the diagnosis using another test that involves drinking a sugar solution followed by several blood-sugar-level measurements. Treatment usually involves nutritional counseling, regular exercise and weight loss if you are obese. If these measures do not lower blood glucose levels sufficiently, insulin may be needed to control gestational diabetes.

What to Do

If you have any risk factors for gestational diabetes, you should work with your doctor to try to modify those factors that you can, such as losing excess weight -- even before you are pregnant -- through exercise and healthy eating. If you smoke, quit. If you experience any symptoms that could indicate the development of gestational diabetes, call your doctor immediately. These symptoms include increased urination, thirst and/or appetite, decreased energy and weight loss.

Self-Care Steps for Diabetes

• Follow your doctor's recommendations for diet and exercise.

• Your treatment might include daily blood glucose testing.