Women who are physically abused during pregnancy may be at increased risk of delivering prematurely, researchers found.

The findings suggest that obstetricians should routinely ask women about domestic violence, they note in a report in the American Journal of Obstetrics & Gynecology.

The study included 2,660 Portuguese women who were interviewed shortly after giving birth between 1999 and 2000. Of the 217 women who delivered prematurely, one-quarter acknowledged that they had ever been hit, slapped, kicked or otherwise physically abused - usually by their partner.

That compared with 8 percent of women whose pregnancies had gone to term.

In Portugal, as in many countries, pregnant women are not routinely screened for domestic abuse, note the researchers, led by Dr. Teresa Rodrigues of the University of Porto Medical School.

However, they say, the new findings suggest that abuse should be considered a risk factor for preterm birth, and that doctors should ask pregnant about it.

The American College of Obstetricians and Gynecologists recommends that obstetricians routinely screen pregnant women for domestic abuse. But at least one survey has found that many doctors don’t ask those questions, though they are more likely to when they suspect abuse.

According to Rodrigues and her colleagues, physical abuse may sometimes lead to preterm delivery directly, from trauma to the abdominal area, for instance. But severe psychological distress may be a significant factor as well.

Such stress may cause hormonal changes that contribute to preterm delivery, the researchers explain. On the other hand, abused pregnant women may be more likely to drink, smoke or use illegal drugs, all of which could raise the risk of premature birth.

SOURCE: American Journal of Obstetrics & Gynecology, February 2008.