1. Women who exercised during pregnancy were more likely to have a vaginal delivery and less likely to develop gestational diabetes or a hypertensive disorder.
2. In normal weight women at low risk for preterm birth, participation in an aerobic exercise regimen during pregnancy did not increase the likelihood of preterm birth.
Evidence Rating Level: 1 (Excellent)
Study Rundown: In the United States, preterm birth at <37 weeks gestational age is the leading cause of perinatal mortality, making prevention of preterm birth a public health priority. Previously, it was believed that exercise during pregnancy was associated with an increased risk of preterm birth and pregnancy loss. In recent years, however, this theory has evolved, especially in the wake of increasing rates of overweight-related pregnancy complications like gestational diabetes and hypertensive disease. Currently both the Center for Disease Control (CDC) and the American College of Obstetrics and Gynecology (ACOG) recommend pregnant women aim for 20-30 minutes of aerobic exercise most days of the week. Given the historical controversy surrounding the topic, researchers in this study conducted a systematic review and meta-analysis of randomized controlled trials to evaluate the effects of exercise during pregnancy on preterm birth.
Exercise in pregnancy was not associated with an increased incidence of preterm birth. Normal-weight women who exercised during pregnancy were more likely to have a vaginal delivery and less likely to develop gestational diabetes and hypertensive disorders than controls. Strengths of this study included large sample size permitted by a pooled meta-analysis and the low risk of bias of included studies. While the control group was not involved in a planned exercise program, it’s possible that participants were involved in outside exercise, which could have biased results toward the null (underestimate of the effect of exercise on preterm birth incidence). Replication of results would lend credence to the findings presented herein; future studies might also examine how exercise impacts birth outcomes in underweight, overweight, or obese individuals and in a population specifically at high risk for preterm birth (e.g. women with a history of prior preterm birth).
Relevant Reading: Aerobic exercise for women during pregnancy
In-Depth [systematic review and meta-analysis]: After a review of major U.S. study databases, researchers preformed a meta-analysis of all data from the nine existing randomized clinical trials that included pregnant women <23 weeks gestational age randomized to an aerobic exercise regimen (n = 1022) or control (n = 1037). On average, exercise programs were 35-90 min, 3-4 times per week. Most women were of normal weight with uncomplicated, singleton pregnancies. The primary outcome was preterm birth (<37 weeks gestational age).
There was no difference in incidence of preterm birth (4.5% vs. 4.4%; 95% CI: 0.68-1.50) or mean gestational age at delivery between the 2 groups. Women in the exercise group were more likely to have a vaginal delivery (73.6% vs. 67.5%; 95% CI: 1.04-1.15) and less likely to have a cesarean delivery (17.9% vs. 22%; 95% CI: 0.69-0.97) than controls. Women in the exercise group were less likely to develop gestational diabetes or hypertensive disorders. There was no difference in birth weight between the 2 groups.
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