Poorly managed diabetes during pregnancy can cause a variety of negative scenarios, including birth defects, stillbirths and miscarriages. Now experts are gravely concerned that the number of women who start their pregnancies with diabetes has doubled in recent years.

According to a startling study performed by Kaiser Permanente researchers, the number of women who had diabetes by the time they conceived doubled over a span of just six years. The study, which appears in the May edition of Diabetes Care, was performed between 1999 and 2005 and was one of the largest-ever health surveys of expectant mothers.

In some age groups, the results were even worse. Researchers found that the number of teenagers who had diabetes before birth jumped fivefold.

"These are high-risk pregnancies," says Dr. Florence Brown, an expert on pregnancy and diabetes. "All women with pre-existing diabetes need to plan their pregnancies."

The rise of diabetes among women of childbearing age mirrors the prevalence of the disease in the general population. The most common form of diabetes is type 2, which is linked to obesity.

"It's important to recognize with the increase in overweight and obesity, more women than ever will be entering their reproductive years with diabetes," says study author Jean Lawrence, a research scientist at the Kaiser Permanente Bellflower Medical Center in Bellflower, Calif.

Pre-pregnancy diabetes is different from gestational diabetes, a temporary condition that some women develop during pregnancy. Doctors say pre-pregnancy diabetes represents a greater threat to the growing 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. (But) with excellent care, these women have an excellent chance of having a healthy baby."

Significant Jumps Among All Groups

The new study, which included 175,249 women who gave birth from 1999 to 2005, included women with type 1 and type 2 diabetes. All of the women in the study were treated at one of 11 Kaiser Permanente hospitals in Southern California. Fifty-two percent of the women were Hispanic, 26 percent were white, 11 percent were Asian/Pacific Islanders, and 10 percent were black, according to the study. The study found significant jumps in pre-pregnancy diabetes in every age, racial and ethnic group.

In 1999, the rate of diabetes was 0.81 per 100 births; by 2005, that number had jumped to 1.82 per 100 births.

The rates of gestational diabetes have stayed the same, according to the Kaiser study. What did change during the study period was the proportion of preexisting diabetes compared to gestational diabetes. In 1999, of all pregnancies affected by diabetes, 10 percent were due to preexisting diabetes, while 90 percent were due to gestational diabetes. In 2005, 21 percent of women had preexisting diabetes, compared to 79 percent with gestational diabetes, according to the study.

"We saw an increase in type 2 diabetes. That's due to the increase in overweight and obesity. Also, type 2 is being diagnosed at younger ages," says Lawrence, who suggested that women do whatever they can to reduce their risk of type 2 diabetes by eating a healthful diet, maintaining a proper weight and being active. She said there's no known way to prevent type 1 diabetes.

Steps Women Can Take

"There are things women can do before they become pregnant that will increase the likelihood of them having a healthy baby," Lawrence said. That includes controlling blood sugar levels with an insulin pump or maintaining a healthy diet and exercise routine. Overweight women are also encouraged to shed some pounds before getting pregnant.

The North Shore-Long Island Jewish Health System in New York has a special program to help moms-to-be manage their diabetes. Women are encouraged to seek medical help at least three months before they plan to have a baby so doctors can help them control their blood sugar and increase their intake of folic acid, says program manager Marie Frazzitta.

"By the time a woman knows she is pregnant, the (baby's) heart is already developed," Frazzitta says. At that point, "there's not much we can do."