MONDAY, April 28 (HealthDay News) -- The number of women starting their pregnancies with type 1 or type 2 diabetes has doubled since 1999, but rates of gestational diabetes have stayed the same, new research finds.

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

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

And, she added, "having diabetes during pregnancy increases the risk of miscarriage early in pregnancy and the risk of stillbirth later in pregnancy. It also increases the chances of having a baby with birth defects, and it may result in larger babies and more difficult deliveries."

Results of the study are published in the May issue of Diabetes Care.

Past research has focused on the number of women who develop diabetes during pregnancy, which is called gestational diabetes, and generally disappears after the baby is born.

The new study, which included 175,249 women who gave birth from 1999 to 2005, also 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.

Preexisting diabetes -- type 1 or type 2 -- was found in 1.3 percent of all pregnancies. In 1999, the rate of preexisting diabetes was 0.81 per 100 births; by 2005, that number had jumped to 1.82 per 100 births.

But, during that six-year period, gestational diabetes rates remained nearly unchanged. In 1999, 7.5 women per 100 births had gestational diabetes; in 2005, it was 7.4 women per 100 births.

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.

The researchers also noted some differences in race and age. Black, Hispanic and Asian/Pacific women were more likely to have diabetes before birth, and teens and women over 40 experienced dramatic jumps in their pre-pregnancy diabetes rates. Teen mothers saw a fivefold increase in preexisting diabetes, while mothers over 40 saw a 40 increase in the rate of pre-pregnancy diabetes.

Experts blame much of the increase on the rising trend of overweight and obesity.

"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," said 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.

Dr. Stuart Weiss, an endocrinologist at the New York University Langone Medical Center, said he "was surprised that the incidence of gestational diabetes wasn't up."

For women who know they have diabetes before pregnancy, Weiss advised: "Control your blood glucose levels as aggressively as possible. Control isn't easy to do, because you have to have adequate nutrition and still control your blood sugar."

But, he added, it's crucial to try, because it may help prevent some of the serious complications associated with diabetes.

More information

To learn more about diabetes and pregnancy, visit the U.S. Centers for Disease Control and Prevention.

SOURCES: Jean Lawrence, Sc.D., M.P.H., research scientist, Kaiser Permanente Bellflower Medical Center, Bellflower, Calif.; Stuart Weiss, M.D., endocrinologist and clinical assistant professor, New York University Langone Medical Center, and School of Medicine, New York City; May 2008, Diabetes Care

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