NEW YORK (Reuters Health) - A mother who contracts influenza, pneumonia, or a sexually transmitted disease around the time of pregnancy appears to be at increased risk of having a child that will develop leukemia, new research shows.

These observations "suggest that maternal infection might contribute to the develop of childhood leukemia, which has been postulated to have an infectious origin," Dr. Marilyn L. Kwan, from the Division of Research at Kaiser Permanente in Oakland, California told Reuters Health.

As reported in the American Journal of Epidemiology, Kwan and her colleagues studied 365 children diagnosed with childhood leukemia and 460 similar children without cancer. Data on maternal illnesses and drug use from before pregnancy through breastfeeding were obtained by interview with the mother.

The investigators found that a maternal history of influenza or pneumonia that occurred between 3 months before conception through the end of breastfeeding raised the risk of leukemia in the child as much as 89 percent.

A maternal history of sexually transmitted disease, such as herpes or chlamydia, had an even stronger effect on the risk of childhood leukemia, increasing the odds by more than sixfold.

By contrast, women who used iron supplements around the time of pregnancy had a decreased of having a child with leukemia.

"Overall, these results emphasize the importance of maintaining good health while pregnant, which has always been an overarching policy promoted by (doctors) in order to have a smooth pregnancy and healthy baby," Kwan concluded.