Pregnant women who take a daily baby aspirin may reduce the risk for premature birth.

Researchers did a randomized, double-blinded placebo-controlled study of 11,976 women in six countries with high rates of premature birth: India, the Democratic Republic of the Congo, Guatemala, Kenya, Pakistan and Zambia. Beginning in the first trimester of pregnancy, half the women received a daily 81 milligram aspirin tablet, while the rest took a placebo.

Compared with those who took a placebo, the women who took aspirin had an 11 percent lower relative risk of giving birth before 37 weeks and a 25 percent lower risk of delivering earlier than 34 weeks. The rate of fetal or infant death from 20 weeks gestation to seven days postpartum was 14 percent lower in those whose mothers took aspirin. The study is in Lancet.

The lead author, Dr. Matthew K. Hoffman, chairman of obstetrics and gynecology at Christiana Health in Newark, Del., said that early preterm birth is driven by inflammation, for which aspirin is an effective treatment.

Dr. Hoffman stressed that the trial was restricted to low and middle-income countries and to first-time pregnancies with singleton babies. Still, he said, aspirin is safe and inexpensive and would probably be useful in all countries. “It does mean taking a daily medication, which women are understandably reluctant to do. But our study shows that aspirin would benefit most children.”

Those considering a daily aspirin should check with their doctors, experts advise, since aspirin can cause bleeding and other side effects.