Health A-Z

Medical Content Created by the Faculty of the
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 percent of all pregnant women in the United States. It is more common in African-American, Latino, Native American and Asian women compared with 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, larger quantities of the 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 non-pregnant 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.