Vigorous leisure activity and pregnancy outcome.

Background: Preterm birth is the leading cause of perinatal mortality in North America and Europe and a major predictor of neonatal and infant morbidity. Postterm birth is associated with increased infant mortality and morbidity, as well as increased frequency of surgical or induced labor. Because vigorous leisure activity may affect timing of delivery, this study examined association between vigorous leisure activity and birth outcomes.

Methods: Women (N = 1,699) with a singleton pregnancy were recruited at 24-29 weeks' gestation from prenatal clinics in central North Carolina between 1995 and 1998. The type and duration of any regular vigorous leisure activity was assessed in a telephone interview covering the 3-month period before pregnancy and during the first and second trimesters of pregnancy.

Results: The prevalence of vigorous leisure activity was 22% before pregnancy, 14% during the first trimester, and 8% during the second trimester. Vigorous leisure activity before pregnancy was unrelated to preterm (<37 weeks) as compared with term delivery (37 to <42 weeks). The risk of preterm birth was somewhat reduced with vigorous leisure activity during the first trimester (odds ratio = 0.80; 95% confidence interval = 0.48-1.35) and more so during the second trimester (odds ratio = 0.52; 95% confidence interval = 0.24-1.11). Vigorous leisure activity before pregnancy or during the first or second trimester was not associated with postterm delivery (>/=42 weeks).

Conclusions: Vigorous leisure activity during the first trimester, and even more so in the second trimester, was associated with a reduced risk of preterm birth. There was no association with postterm birth. To address the etiologic role of activity on pregnancy outcome and to overcome self-selection, a randomized clinical trial would be needed.