Fetal responses to maternal strength conditioning exercises in late gestation

Cardiovascular responses to strength conditioning exercises were examined in 12 healthy pregnant women and their unborn fetuses during the third trimester. A group of 12 healthy nonpregnant women of similar ages, parity, body height, and pre-pregnant body mass was also studied. Maternal heart rate and blood pressure and fetal heart rate (FHR) responses were measured in both the supine (30 degrees tilt) and seated postures during handgrip (HG), single-leg extension (SL), and double-leg extension (DL) exercise. Subjects performed 3 sets of 10 reps at 50, 70, and 90% of their 10-repetition maximum (10-RM) for each exercise in both postures. Pregnant subjects exhibited higher heart rates but similar blood pressure responses to control subjects under all experimental conditions. Significant increases were observed for the frequency of FHR accelerations (0.10 to 0.27/min) from rest to DL in the sitting posture at 90% RM. Moderate fetal bradycardia was observed occasionally in the tilted supine posture at rest and both during (SL, DL) and following (HG, SL, DL) exercise, suggesting that this posture should be avoided in late gestation. The results support the safety of moderate strength conditioning exercises in healthy pregnancy.