Having poorly controlled diabetes while pregnant can cause all sorts of harm, from stillbirths and miscarriages to birth defects. So experts are concerned that the number of women who already have diabetes by the time they conceive is rising rapidly: Between 1999 and 2005, the group doubled in size, growing significantly across all age, racial, and ethnic groups examined by Kaiser Permanente Southern California researchers, who report their findings in May's Diabetes Care. Different from gestational diabetes, a temporary type that some women develop well into pregnancy, prepregnancy diabetes can pose more of a threat to a developing fetus.
"A baby's organs form during the first five to eight weeks of pregnancy," says Steven Gabbe, dean of the Vanderbilt University School of Medicine and an obstetrician who specializes in diabetes and pregnancy. "If a mother's diabetes is poorly controlled, she can have up to a 25 percent risk of delivering a baby with a major malformation of the heart, brain, or skeleton."
The good news, says Gabbe: "With excellent care, these women have an excellent chance of having a healthy baby." The way for diabetic women to reduce the risks is to get their blood sugar levels in check before becoming pregnant, then keep those levels close to normal throughout. Although there's no known way to prevent type 1 diabetes—characterized by the body's inability to produce insulin, which converts blood sugar into energy needed for survival—type 2 diabetes can be warded off or controlled through a healthful diet, weight loss, and exercise. All are especially important as a defense for women who've had gestational diabetes during past pregnancies.
Before pregnancy, advises endocrinologist Sue Kirkman, vice president of clinical affairs at the American Diabetes Association, women should get tested for diabetes if they're overweight and have one of the following risk factors: an inactive lifestyle; a family history of diabetes; an African-American, Hispanic, American Indian, or Asian/Pacific Islander heritage; or a prior history of gestational diabetes. For women who've had gestational diabetes, Kirkman advises annual diabetes tests, as well as one at the first prenatal visit of each subsequent pregnancy.
"I think the main message is just for women to be aware of their risk factors and get tested hopefully before they get pregnant so there's plenty of time to know they have diabetes and get it under control," Kirkman says. Unfortunately, she notes, more than half of all pregnancies are unplanned, and many women unknowingly develop diabetes, as symptoms of type 2 aren't always obvious.
"For women who already have diabetes, the main thing is planning the pregnancy," Kirkman says. "The stakes are pretty high."
Since gestational diabetes usually develops late in pregnancy, it doesn't cause the birth defects that pre-existing diabetes can. However, "there are risks associated with having gestational diabetes as well," cautions study author Jean Lawrence, a research scientist at Kaiser Permanente. Marked by a buildup of glucose in the bloodstream, it can fatten babies, making them difficult to deliver and possibly necessitating a cesarean, and it can also set them up for future health problems. Even though gestational diabetes tends to disappear following delivery, women who have it are much more likely to do so again in later pregnancies; they're also more likely to develop type 2 diabetes down the road.
Corrected on 8/5/2010: A previous version of this story incorrectly spelled Kaiser Permanente.