The effects of high- and medium-intensity exercise on the fetus and on the onset and length of labor, birth weight, and Apgar score were studied in healthy athletes who performed a high level of exercise before conception.

Below is a table of 42 women were recruited to the study by newspaper ads and through acquaintances (also known as snowball sampling). They elected to follow either a high- or a medium-intensity exercise program throughout pregnancy until 6 weeks after delivery. Below is a table comparing the two different exercise regimes medium-intensity (MEG) and high-intensity (HEG) on selected neonatal characteristics.

Table III. Effect of medium- and high-intensity exercise during pregnancy on maternal and neonatal characteristics MEG HEG Parameter No. Mean SD No. Mean SD Maternal weight (kg) Week 17 during pregnancy 20 65.8 9.3 20 64.4 6.1 Six weeks after labor 20 64.6 9.2 19 63.2 6.1 Skinfold thickness (mm)* Average during pregnancy 60 56.9 16.6 58 54.7 13.4 Six weeks after labor 20 55.2 15.9 20 53.9 127 Onset of labor (wk) All women 21 39.9 1.2 21 39.6 1.6 Primiparous women 19 39.8 1.2 15 39.7 1.5 Secundiparous women 2 40.0 0 5 39.2 1.9 Multiparous women 1 41 Duration of labor (hr) Normal delivery 17 6.7 55 18 9.4 5.9 Instrumental deliveryt 8.0 2.6 11.7 3.4 Cesarean section Not recorded 1 Not recorded Birth weight (gm) 21 3590.5 532 21 3650.7 515.8 Placental weight (gm) 20 643.3 137.2 19 709.7 88.7 1 min Apgar score 21 8.4 0.9 21 8.8 0.6 5 min Apgar score 21 9.1 0.5 21 9.4 0.5 MEG, Medium-intensity exercise group; HEG, high-intensity exercise group. "Sum of skinfolds of triceps, suprailiac, and thigh. #Vacuum or outlet forceps. (In medium-intensity group, two vacuum and one outlet forceps; in high-intensity group, one vacuum and one outlet forceps.)