As a result of a number of recent studies on exercise in pregnancy, the debate over the risks of aerobic exercise in pregnancy has waned. In January 2002, the American College of Obstetricians and Gynecologists (ACOG) issued an opinion report stating that “In the absence of either medical or obstetric complications, 30 minutes or more of moderate exercise a day on most, if not all, days of the week is recommended for most pregnant women.”1 While common sense and a number of smaller observational studies and controlled trials support this recommendation, a Cochrane review,2 published in the same month as the ACOG opinion, concluded that there is insufficient evidence of benefit or harm to mother or fetus to make a recommendation regarding aerobic exercise in pregnancy. According to the review, the available studies were too small, flawed in their design, and inconsistent in their methodology and outcome measures to support a recommendation. Specific benefits of regular exercise to mother and fetus have yet to be confirmed.
The recent ACOG Committee Opinion signals a welcome interest in the benefits of regular aerobic exercise in pregnancy and a trend away from focusing on a variety of theoretic risks to mother and baby. In terms of positive benefits, the Cochrane reviewer found that women who exercised regularly during pregnancy subjectively improved their body image and maintained or improved their physical fitness. No other benefits (or risks) were supported by the currently available studies. Parameters studied include mode of delivery, length of labor, growth parameters, preterm birth, and Apgar scores.
Despite the limitations of current evidence, several studies suggest that smaller babies are born to women who exercise vigorously during pregnancy, as a result of restriction of neonatal fat mass. It also has been suggested that these leaner babies may be less likely to become obese children and adults.3 At the very least, pregnancy is a time when women have regular contact with physicians and may be open to general lifestyle changes that might benefit them. Excess weight gain during pregnancy and postpartum weight retention are associated with increased rates of maternal obesity eight to 10 years later.4
Given the current epidemic of obesity and the associated rising incidence in rates of the metabolic syndrome and type II diabetes, it would seem that well-designed, large-scale prospective clinical trials of exercise in pregnancy should be high on the national research agenda, in line with priorities established by Healthy People 2010. Long-term follow-up of the exercising women and their infants could help to clarify the real benefits versus the risks of exercise during pregnancy and allow future recommendations to be based on evidence rather than expert opinion.
For many women, the perceived benefits of physical fitness and enhanced body image provide enough reason to continue to exercise during pregnancy. However, little has been published about the acceptability of exercise in pregnancy to women of diverse cultural backgrounds. Given the high prevalence of obesity and overweight among women in some population subgroups,5 it even may be desirable to provide extra encouragement to exercise during pregnancy, as well as in general. However, successful implementation of the recent ACOG recommendations will require that women find the idea of exercising during pregnancy to be culturally acceptable. Therefore, understanding the attitude of women from diverse backgrounds toward exercise in pregnancy is important.
Given ACOG's statement that potential risks are rare in properly screened pregnant women who avoid extreme environmental conditions and activities that can lead to abdominal trauma, moderate aerobic exercise appears to be a safe, affordable way to improve a woman's sense of well-being during pregnancy. The shift in attitude away from viewing aerobic exercise as a potential hazard to healthy pregnant women is a breath of fresh air. We look forward to the day when sound evidence supports more definitive guidelines about exercise in pregnancy.