Abstract
Objective: To examine the association between exercise during pregnancy and preterm birth (PTB).
Design : Retrospective cohort analysis.
Setting : Jinan, China.
Population : Singleton live births from December 2018 to December 2019.
Methods: Questionnaires contained items about physical exercise (frequency, time, and primary exercise patterns) during pregnancy and each trimester. Adjusted odds ratios (OR ) were estimated using logistic regression. Variable selection for the multivariate models was guided by the directed acyclic graph. The median effect was analyzed by the sequential test.
Main Outcome Measures : PTB.
Results: The prevalence of PTB in this study was 4.38% (285/6501). The adjusted OR (95% CI ) for the risk of PTB related to exercise during pregnancy was 0.74 (0.58-0.95). During the 1st and 2nd trimesters, the OR s (95% CI ) for 2.5 to 7 hours of exercise per week were 0.77 (0.59-0.99) and 0.74 (0.57-0.96). During the 3rd trimester, the OR s (95% CI ) for 2.5 to 7 hours and more than 7 hours of exercise per week were 0.74 (0.56-0.96) and 0.65 (0.44-0.94). After stratifying the subjects, the association was only found among subjects without pregnancy complications. Pregnancy complications partially mediated (52.40%) the relationship between exercise during pregnancy and PTB.
Conclusions: Exercise during pregnancy was a protective factor of PTB for women without pregnancy complications. 2.5 to 7 hours of exercise (like walking) per week may be appropriate in three trimesters of pregnancy, and the time could be extended in the 3rd trimester.
Keywords : Preterm birth; Exercise; Pregnancy; Trimester; Mediation analysis
Tweetable abstract: Women who exercised during pregnancy were at decreased risk of PTB. 2.5 to 7 hours per week may be appropriate in three trimesters of pregnancy, and the time could be extended in the 3rd trimester.