Regular exercise during pregnancy offers overall health benefits, Dr. Ruben Barakat, at Universidad Politecnica de Madrid in Spain, and colleagues note in the American Journal of Obstetrics and Gynecology. However, few investigations have focused on the effects of resistance-type exercise during pregnancy and whether this alters actual childbirth.

Therefore, they compared delivery outcomes after supervised toning and resistance exercises for shoulders, arms, pelvis, and legs, plus toning and mobilization of associated joints, in 80 women during mid to late pregnancy, compared with 80 non-exercising peers.

All of the women previously obtained less than 20 minutes of exercise on 3 or fewer days each week, a low level of exercise the "controls" maintained. By contrast, the exercise group participated in 3 weekly toning and resistance sessions of less than an hour each from pregnancy week 12 or 13 through delivery.

There were no adverse effects noted in the 72 exercising women or the 70 controls that completed the study. And, in contrast to a previous report of increased vaginal delivery associated with regular exercise during pregnancy, Barakat's team found no differences in delivery mode between the groups

Fifty-one exercisers delivered vaginally, another 10 had a delivery requiring instruments, and 11 had Cesarean, compared with 50, 9, and 11, respectively, in the non-exercisers. The groups also similarly required epidural anesthesia and had similar average durations of complete dilation and delivery, and their newborns were similarly healthy.

"Women in the training group were rather pleased with the exercise training," Barakat and colleagues note in their report. This finding, coupled with the exercisers desire to be physically active during future pregnancies, and the lack of exercise complications, supports the overall benefits of supervised, light-intensity exercise during pregnancy, they conclude.