Smoking during pregnancy may cause the placenta to prematurely detach from the uterus wall, putting both the mother and fetus at risk of death, researchers say.

Reuters reported Aug. 3 that researchers found that women who smoked during pregnancy raised their risk of placental abruption, which can cause severe bleeding and results in the death of approximately 40 percent of infants involved.

Moreover, smokers who had a previous abruption had nearly an 11-times greater risk of having another, whereas the risk of a second abruption for nonsmokers was about 5 times greater.

Researcher Cande V. Ananth of the Robert Wood Johnson Medical School said the findings add another good reason for women not to smoke during pregnancy.

The study appears in the Aug. 1, 2007 issue of the American Journal of Epidemiology.