PHYSICAL-ACTIVITY AND PREGNANCY OUTCOME - REVIEW AND RECOMMENDATIONS

The dual stresses of pregnancy and exercise may create conflicting phy siological demands that could adversely affect pregnancy outcome, Spec ifically redistribution of uterine blood flow and subsequent fetal hyp oxia, hyperthermia and the risk of teratogenic effects, decreased carb ohydrate availability for the fetus, and increased uterine contractili ty with a possible increase in risk for pre-term labour, all pose pote ntial threats to fetal growth and development. However, despite these potential risks, literature dealing with exercise and pregnancy outcom e generally shows neutral or somewhat favourable effects. A few studie s have found reduced birthweight, shortened gestation, and less gestat ional weight gain among women who continue vigorous exercise during pr egnancy compared with those who discontinue exercise or who are sedent ary. However, most studies find little, if any, association between ex ercise and birthweight or gestational age, In contrast, studies of occ upational physical activity often show an association between heavy ph ysical work and lower birthweight and shorter gestation, especially in women in developing societies whose nutritional status may be comprom ised, Standing, in particular, may be associated with increased risk o f prematurity. Although other outcomes, such as length of labour, type of delivery have not been well studied, there is no indication of any negative associations with exercise. There is limited evidence which suggests that exercise is related to shorter labour and is a useful tr eatment for gestational diabetes. Exercise is also associated with few er symptoms and discomforts of pregnancy, This relationship is tempora l in that exercise earlier in pregnancy is associated with fewer sympt oms later in pregnancy. The lack of evidence for any harmful effects o f exercise on pregnancy outcome indicates that, for healthy, well-nour ished women, exercise during pregnancy is safe and subject to few rest rictions. This conclusion is reflected in the revised, 1994 recommenda tions of the American College of Obstetricians and Gynecologists.