Statistical analysis
Statistical analysis was performed using SPSS for Windows, version 25.0.
A two-sided p-value of <0.05 indicated statistical
significance. Continuous variables are presented as median
(interquartile range) and categorical variables as number and
percentage. Significance between groups was assessed by the McNemar test
for categorical variables and the paired-samples t-test for continuous
variables with a normal distribution. Wilcoxon rank sum test, a
non-parametric test, was performed for continuous variables with
non-normal distribution. Multivariable logistic regression, after adjust
for confounders (presented in DAG), was performed to identify risk
factors associated with sPTB. Kaplan–Meier curves were generated for GA
at delivery according to the different subgroups (cervical dilation
< 3cm and ≥ 3cm) and compared using the log-rank test to
assess the prolongation of pregnancy observed in each subgroup.