Strengths and Limitations
One of the strengths of this study is its focus on the effects of extremely long IPIs, which is in accordance with the current birth policy in China. Our results suggest that shorter and longer IPIs should be a risk factor in subsequent pregnancy for women with a history of CS. In addition, our analysis of the adverse pregnancy outcomes related to IPI is relatively systemic, comprising scar-related morbidities and common pregnancy morbidities.
The main limitation of our study is its retrospective design, which precludes a power analysis. Moreover, the rate of trial of labor after cesarean (TOLAC) was only 2.87% (n = 47), and the incidence of uterine rupture may be underestimated. We could not accurately analyze the effects of IPI on the success of VBAC or the risk of uterine rupture for the small proportion of women with TOLAC. A larger, prospective study would have to be carried out to identify candidates for TOLAC and provide intensive prenatal care to guarantee safety during TOLAC. Our previous systematic evaluation found that an IPI of more than 6-8 months after CS can reduce the risk of adverse maternal and neonatal outcomes, which is quite different from the results of this study. Our conclusions regarding a short IPI are based on a small sample size and should thus be interpreted with caution. Given that the WHO recommends an IPI of ≥24 months, further studies of a short IPI would have to be in a prospective design.