For years pregnant women have been told that walking at a moderate pace is a good way to stay healthy during pregnancy. Now, a new study reports that for some women, stretching may be more effective than walking or vigorous exercise when it comes to reducing the risk of the high blood pressure and related problems associated with pregnancy — also known as preeclampsia.

Preeclampsia occurs in about 8% of women overall and in about 15% of high-risk pregnancies. It usually develops after the twentieth week of pregnancy and is more commom among African-American women and women carrying twins. Symptoms include high blood pressure of at least 140/90, swelling of the hands and feet and protein in the urine. Women who develop preeclampsia often are hospitalized and require bed rest for the remainder of their pregnancy. Left untreated, preeclampsia can be life threatening to both mother and baby. The condition normally disappears after delivery.

The new study, by researchers at the University of North Carolina at Chapel Hill School of Nursing and led by associate professor SeonAe Yeo, looked at a group of sedentary pregnant women who had experienced preeclampsia during a previous pregnancy. Beginning at week 18 of their current pregnancy, half the women were instructed to walk five times a week for 40 minutes at a moderate pace. The other half were instructed to do slow, controlled, non-aerobic stretching exercises that were taught on a 40-minutes exercise video.

By the end of their pregnancies, about 15% of the group that walked had developed preeclampsia, but less than 5% of the group that did the stretching exercises developed the condition. As Professor Yeo puts it, "Clearly, walking does not have a harmful effect during pregnancy, but for women who are at high risk for preeclampsia, our results may suggest that stretching exercises may have a protective effect against the condition."