The number of women with diabetes giving birth more than doubled recently, a finding that raises health concerns for both mothers-to-be and babies.

The statistics coincide with an epidemic of type 2 diabetes that has increased as Americans pack on the pounds.

"We're seeing more people who are overweight and obese, and that's a key risk factor for type 2 diabetes," said Jean Lawrence, lead author of the research, published in the May issue of Diabetes Care.

Lawrence and her colleagues at the Kaiser Permanente Department of Research & Evaluation in Pasadena, Calif., studied 175,249 women and teens who had given birth in 11 Southern California Kaiser hospitals between 1999 and 2005. They checked to see how many women had a diagnosis of type 1 or type 2 diabetes before giving birth.

The team discovered a rapid rise in the number of women giving birth with diabetes during the seven-year period — from 245 women in 1999 to 537 in 2005. The researchers suspect that most of the increase can be attributed to women or teenage girls who've gained weight and developed type 2 diabetes, the most common form of the disease.

Women or teens who've just developed type 2 diabetes might get pregnant before they know they have the disease, said Sue Kirkman, a vice president for clinical affairs at the American Diabetes Association.

Or sometimes women who already have a diagnosis of either type 1 or type 2 diabetes don't keep blood sugar levels under control.

Women who get pregnant under such conditions have elevated blood sugar levels, which puts them and the developing fetus at risk, Lawrence said. Women who get pregnant with out-of-control diabetes are more likely to have a miscarriage or suffer from preeclampsia, a dangerous form of high blood pressure that strikes in pregnancy.

Developing babies exposed to high blood sugar levels can suffer from birth defects, including heart defects, Lawrence added.

Overweight women or women with a family history of diabetes should get their blood sugar levels checked before trying to get pregnant, Kirkman said. Many women don't realize they are pregnant at first and don't get a chance to curb sugar levels early enough to prevent birth defects that occur in the first trimester, she said.

Once the disease is diagnosed, women should work with a doctor to get sugar levels under control.

Women who do so have a better chance of having an uneventful pregnancy and delivering a healthy baby, Lawrence said.