There is a prevailing belief that exercise during pregnancy, particularly vigorous exercise, increases the risk of preterm birth. A Cochrane review concluded that trials on exercise were too few and too small to support a recommendation. Cohort studies have found no association between exercise and preterm birth, or a possible reduced risk. Recent results from the Danish National Birth Cohort showed that in almost 90,000 pregnancies, a little more than a third of mothers engaged in physical exercise during early pregnancy, fewer during late pregnancy. All exercisers had a moderately reduced risk of preterm birth. These findings confirm current exercise guidelines in force in the US, UK, Denmark and Norway, which are based on health benefits for the mother – prevention of obesity, gestational diabetes, and preeclampsia. The findings also call into question the practice of bed rest to avoid preterm birth. Here are the European guidelines, which are essentially the same as US guidelines.
·Pregnant women should engage in “moderate to somewhat hard” exercise at least 30 minutes a day (US guidelines say “on most days”).
·Pregnant women who do not exercise are encouraged to start light fitness training (e.g. brisk walking and strength training)
·Pregnant women who are accustomed to “hard fitness training” need not stop as long they remain healthy.
Reference: Juhl M, Andersen PK, Olsen J, et al. (2008). Physical Exercise during Pregnancy and the Risk of Preterm Birth: A Study within the Danish National Birth Cohort. American Journal of Epidemiology 167(7):859-866.