MATERNAL EXERCISE DURING PREGNANCY, PHYSICAL-FITNESS, AND FETAL GROWTH

The value of exercise during pregnancy is controversial; both benefits and risks have been hypothesized. As empiric evidence is scant, the i ssue was investigated in a prospective study that assessed the impact on fetal growth of maternal exercise in each trimester of pregnancy. A cohort of over 800 prenatal patients was recruited from obstetric pra ctices in Pennsylvania and New York between January 1987 and June 1989 Subject were interviewed at entry into care and recontacted at 28 and 36 weeks of gestation. In women with prior adverse outcomes or a lack of conditioning, the associations between maternal exercise and fetal growth were equivocal. In fit, low-risk prenatal patients, exercise w as positively associated with fetal growth. With low-moderate exercise levels, the adjusted mean birth weights were about 100 g higher than in nonexercisers (117 g; 95% confidence interval 17 to 217 g). With he avier exercise, larger birth weight increments were seen, close to 300 g in those who exercised throughout pregnancy at levels of about 2,00 0 kcal/week in energy expenditure (276 g; 95% confidence interval 54 t o 497 g). These results suggest that the guidelines issued by the Amer ican College of Obstetricians and Gynecologists may be too stringent f or well-conditioned, low-risk, prenatal patients. Additional research to define safe limits more precisely seems warranted.