training in pregnant women effects on fetal development and birth objective the effects of high and mediumintensity 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 conceptionstudy design fortytwo women were recruited to the study by newspaper ads and through acquaintances they elected to follow either a high or a mediumintensity exercise program throughout pregnancy until 6 weeks after delivery documentation of their intensity of activity before conception retrospectively during pregnancy and after delivery was obtainedresults there were no differences between the high and mediumintensity exercise group in duration of labor birth weight or 1 and 5minute apgar scores the higher level of exercise correlated with a significantly greater maternal weight gain during pregnancy and significantly earlier onset of labor for those women who gave birth to girls but not for those who gave birth to boysconclusion our results indicate that healthy and wellconditioned women may take part in exercise during pregnancy without compromising fetal growth and development as judged by birth weight or complicating the course of pregnancy or labor