Results
A total of 1854 deliveries with a history of CS were reported at West China Second University Hospital (Sichuan University) between January 1, 2016, and December 31, 2016. According to the exclusion criteria, 192 women were excluded: 51 cases without routine antenatal care, 85 cases of multiple pregnancy, 44 cases of fetal malformation, and 12 cases of uterine surgery other than CS. The final sample size for this retrospective cohort study was 1662, and these women were categorized into 4 groups according to different IPIs: 121 women with an IPI of < 24 months, 583 women with an IPI of 24 to 59 months, 712 women with an IPI of 60 to 119 months, and 246 women with an IPI of 120 months or greater (Figure 1).