MONDAY, May 2 (HealthDay News) -- Obese pregnant women may have a harder time fighting off infections than leaner women do, new research suggests.

Researchers tested the blood of 30 women who were about six months pregnant. Half were obese and had a body-mass index (BMI) of more than 30 prior to becoming pregnant, while half had a normal BMI of 20 to 25.

Obese women had fewer immune system cells that fight infections -- including T-cells and natural killer cells, researchers found. Obese women also had an impaired ability to produce those cells.

The difference could threaten the health of babies born to obese women, study author Dr. Sarbattama Sen, a researcher in the Mother Infant Research Institute at Tufts Medical Center and Floating Hospital for Children in Boston, said in an American Academy of Pediatrics news release.

"Women who are obese before pregnancy have critical differences in their immune function during pregnancy compared to normal-weight women, which has negative consequences for both mother and baby," Sen said.

The issue is taking on added urgency due to the increasing numbers of obese women of reproductive age, Sen added. "Maternal obesity has consequences for the mother and baby, which we are only beginning to understand."

The study was to be presented Sunday at the Pediatric Academic Societies annual meeting in Denver. The data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.

More information

For more about obesity, try the U.S. National Library of Medicine.