Physical activity and the risk of preterm labor: an epidemiological review and synthesis of recent literature.

Considerable recent research effort of physical activity and pregnancy has included evaluation of preterm labor, preterm delivery, and gestational age at delivery. This review specifically evaluates recent studies that included such assessments of gestational parameters. Methodological difficulties (eg, small sample size, selective clinical populations) have prevented clear generalizable findings regarding the impact of physical activity on preterm labor and delivery. The outcomes evaluated are often times not similar from study to study and, with the associated differences in research design, prevent valid meta-analyses of this topic. Because there is some evidence that gestation and birthweight may decrease among physically active women, larger-scale, randomized clinical trials designed specifically to evaluate whether this association is simply a minor change in gestation and birthweight, or if this difference is manifested clinically in higher rates of preterm labor and delivery and low birthweight, are warranted. Without larger, population-based randomized studies, clinicians will remain unclear about the potential risks and/or benefits related to gestational duration of maternal exercise in their populations.