Association of physical activity during pregnancy with labor and delivery in nulliparous patients.

Background: Physical activity during pregnancy is a positive behavior for improving pregnancy outcomes, yet the relationship between physical activity during pregnancy and labor is still debated.

Objective: This study aimed to test our hypothesis that a higher level of physical activity during pregnancy is associated with a shorter labor duration.

Study Design: This was a prospective cohort study of pregnant women with singleton pregnancies and no contraindications to physical activity during pregnancy. physical activity according to type and intensity were evaluated with the Chinese version of the Pregnancy Physical Activity Questionnaire. This questionnaire categorizes physical activities into different types and intensities and quantifies them. The primary study outcome was labor duration. The secondary outcomes were delivery mode, conversion from vaginal delivery to cesarean section, prolonged second stage of labor, perineal tears, episiotomy, and postpartum hemorrhage within 24 hours. Generalized additive models were used to identify both linear and nonlinear relationships between physical activity during pregnancy and labor. A segmented linear model was employed to calculate the saturation effect. Stratified logistic regression was used for subgroup analysis.

Results: In total, 226 women participated in the physical activity survey during pregnancy and gave birth at our hospital. The energy expenditure of physical activity during pregnancy was 145.70 (111.92, 181.69) weekly energy expenditure (MET-h•wk-1). After full adjustment for covariates, a nonlinear relationship was observed between physical activity during pregnancy and the duration of the first stage of labor. Different correlations were observed when the energy expenditure of physical activity during pregnancy was 142.28 MET-h•wk-1. In the two-part regression model, the inflection point of physical activity during pregnancy was at 142.28 MET-h•wk-1. When the energy expenditure of physical activity during pregnancy exceeded 142.28 MET-h•wk-1, each standard deviation increase in physical activity was associated with a decrease of 149.85 minutes in the duration of the first stage of labor (β:-149.85, 95 % CI: -247.54 to -52.17, P = 0.0080).

Conclusions: A nonlinear relationship between physical activity during pregnancy and duration of the first stage of labor ha been identified.When physical activity exceeds 142.28 MET-h•wk-1, each additional standard deviation reduces the first stage of labor by 149.85 minutes. Physical activity is not limited to exercise programs; daily activities such as cleaning, shopping, and walking to and from work are effective ways to increase energy expenditure and help individuals achieve the recommended level of physical activity.