Exercise during pregnancy Dose: Influence on preterm birth outcomes

Background: Preterm delivery typically increases health risk for neonates and is associated with longer infant hospital stay and financial burden. Prenatal exercise dose (frequency, intensity, type, time, volume) have been shown to influence birth outcomes. Increased prenatal exercise dose could therefore provide a critical reduction in health risk and financial burden in preterm neonates.

Objective: It was our aim to explore the effects of prenatal exercise dose from a supervised exercise intervention in pregnant women on the occurrence of preterm (<37 weeks gestation) births, and the impact on health outcomes in preterm neonates.

Study design: This study is a retrospective, secondary analysis of pooled data from three blinded, prospective, randomized controlled trials. Prenatal exercise dose were assessed in supervised aerobic, resistance, and combination sessions throughout pregnancy. In addition to gestational age, birth weight, resting heart rate, neonatal morphometrics (body circumferences, ponderal index), and health status (Apgar-1 and -5) metrics were obtained for 21 women at birth. One-way analysis of variance tests were used to assess the differences between dose grouped as tertiles, while Pearson correlations determined the association between dose and birth outcomes.

Results: Women exercised for an average of 19.6 wks (range: 6 - 21 wks) during pregnancy. Exercise during pregnancy tended to result in later preterm deliveries (p = 0.08). Greater prenatal exercise volume and duration were associated with reduced infant hospital stay post-delivery (p = 0.02). Weekly exercise volume was associated with increased Apgar scores (p = 0.01).

Conclusion: Increased prenatal exercise volume and duration is associated with improved birth outcomes in preterm neonates.