A new study suggests that moderate exercise during pregnancy is safe even for women with chronic illness.

Black women are twice as likely to have premature or low birth weight infants compared with white women, but the reasons why are not clear, Dr. Suezanne T. Orr of East Carolina University in Greenville, North Carolina and her colleagues note.

Evidence on the effects of exercise in pregnancy outcomes has been mixed, and most studies have been done with white women, they add. And little is known about how much women with chronic illness exercise while they are pregnant, Orr and her team note.

To better understand the relationship, Orr and her team followed 922 low-income black women attending prenatal clinics in Baltimore. Twenty-nine percent had diabetes, hypertension or another type of chronic illness, and 32 percent had a poor outcome of a previous pregnancy.

Before pregnancy occurred, 26 percent of the women said they didn’t exercise at all, 44 percent said they did non-strenuous exercise only, 23 percent performed both strenuous and non-strenuous exercise, and 8 percent said they did strenuous exercise only.

During pregnancy, 36 percent didn’t exercise at all, 56 percent performed non-strenuous exercise only, 2 percent did strenuous exercise only, and 6 percent did both type of exercise.

Nearly 14 percent of the women had their infants prematurely, while 12 percent of the babies were low birth weight.

The researchers found no association between a woman’s exercise level and her pregnancy outcome. Even among the women with chronic illness, the researchers found, exercise did not increase the risk of having a premature or low birth weight infant.

They caution that their study only looked at exercise “for fun and fitness,” and did not evaluate the effects of activities like having to stand for long periods at work. “A next step in studies of physical activity during pregnancy might be to separate physical activity by its purpose (eg, fun and fitness, work, childcare) as well as intensity,” they conclude.

SOURCE: Ethnicity and Disease, Autumn 2006.