What it is. High blood-sugar levels, occurring in about 4 percent of pregnant women, which puts the baby at risk of being too big.
What causes it. Your pancreas is unable to produce enough insulin to counteract pregnancy hormones that increase blood-sugar levels.
Symptoms. May include thirst, increased urination, and blurred vision. But women often have no symptoms at all.
Treatment. Most cases can be controlled with a high-fiber diet that's low in sugars, though some women need insulin injections or the drug glyburide. Gestational diabetes usually disappears after delivery, but about half of women with gestational diabetes develop type 2 diabetes later in life.
Can you prevent it? You can reduce your risk by staying at a healthy weight, eating a low-fat, high-fiber diet, and exercising regularly.