The effect of exercise during pregnancy on the risk of preterm birth: A
retrospective study
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 ORs (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 ORs (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