3.2 The characteristics of exercise during each trimester
During the 3rd trimester and throughout pregnancy, the distribution of time spent was statistically different between the preterm and full-term women (P =0.005; P =0.045). The distribution of energy expenditure was statistically different during the 3rd trimester(P =0.007). More details were provided in supplementary material Table S1. Besides, for the patterns of exercise, most subjects (90.64%) chose the option of walking.