Hormonal birth control linked to risk of gestational diabetes

Women who use hormonal contraceptives before they get pregnant may be 1.4 times more likely to suffer from gestational diabetes than women who do not use any method of birth control, a new study suggests. However, experts stress that more research is needed.

"This study provides evidence that hormonal contraceptive methods may increase a woman's risk for GDM (gestational diabetes) in her following pregnancy, even after adjusting for maternal age, race, education and income level, marital status, Medicaid status at delivery, and type of prenatal care received," the researchers wrote in the study, released today by the Centers for Disease Control and Prevention.

"More research is needed to verify contraception as a potential risk factor" for gestational diabetes, they wrote.

Gestational diabetes is a type of diabetes that occurs in a pregnant woman who did not have the disease before becoming pregnant, the CDC explains. Gestational diabetes usually starts in the middle of pregnancy, and it can usually be controlled with a healthy diet and exercise, the CDC says, but in some cases patients also need to take insulin. If the condition is not well controlled, it can cause health problems for both mother and baby. Gestational diabetes usually goes away after the woman gives birth.

In the study, researchers examined data from 2,741 women who completed the 2007 and 2008 Missouri Pregnancy Risk Assessment Monitoring System (PRAMS) survey. The survey is administered in 40 states and in New York City, and it represents about 78 percent of all U.S. live births, monitoring certain experiences of new mothers before, during and after pregnancy.

The women in the study answered questions about their history of gestational diabetes and their pre- and post-pregnancy use of birth control such as tubal ligation, vasectomy, birth control pills, condoms, injections, contraceptive patches, a diaphragm, a cervical ring, an intrauterine device, the rhythm method, withdrawal or another method.

The researchers found that 8.3 percent of the women in the study reported having been diagnosed with gestational diabetes in their most recent pregnancy. Hormonal contraception -- including the pill, patch, injections, cervical ring and IUD -- was the most common form of birth control, used by about 18 percent of the women, followed by barrier methods at about 17 percent.

Dr. Sharon Sutherland at Cleveland Clinic's Department of Obstetrics and Gynecology, who was not involved in the study, told CBS News that the study had certain limitations.

First, it was a retrospective study, based on "information after the fact," she said. Second, it was not clear how exactly the questions about contraception use in the survey were worded , she said, adding that the study did not specify whether the women had been asked about the exact timing and duration of their contraception use. And it did not say if the women had been asked if they were on birth control when they got pregnant.

"That information was missing," Sutherland said. That makes it hard to establish from the study if gestational diabetes risk is indeed related to hormonal contraception use, and therefore further research is needed to examine whether one is really related to the other.