Statistic
Data analysis was performed with SPSS 21.0 software(IBM SPSS Statistics for Windows, IBM, USA). Student’s t -test and Mann-WhitneyU -test were used to compare continuous variables with and without normal distribution between the two group. The Chi-square and Fisher’s exact tests were used for categorical variables. Cox survival regression was conducted to compare the proportion of women undelivered after the procedure.We used logistic regression to analyze risk factors associated with adverse pregnancy outcomes. Differences were considered significant when P < 0.05.