There are conflicting results regarding exercise in pregnancy and the incidence of pregnancy and the incidence of preterm labor and length of gestation. Several large, prospective, observational studies, supported by smaller, randomized trials and meta-analyses, found no increase in preterm labor and a similar gestation age at delivery in women who exercised during pregnancy as compared to controls. One study suggested no difference in preterm labor but slightly shorter gestation. This study found that women who continue to exercise during pregnancy have gestations that are an average of 5 days shorter than women who did not exercise during pregnancy, with no increase in preterm delivery.
Other markers of fetal well-being have also been studied in exercising gravidas. No negative impact on 1-or5-minute Apgar scores has been identified. In fact some studies suggest improved Apgar scores. These findings may be influenced by confounding factors in the group of women who continue to exercise during pregnancy. Two studies found a significant decrease in cord abnormalities (nuchal cord and true knot in the cord) in women who continued to exercise during pregnancy as compared with women who did not. A limited number of observational studies reported no apparent adverse outcomes in women who exercised at intensities and durations above ACOG recommendations.