Statistical analysis
Variables were checked for normal distribution by Kolmogorov-Smirnov
test. Comparisons between cases with and without adverse neonatal
outcomes were performed by Student-T (assuming unequal variances),
Mann-Whitney U, Pearson Chi-squared and Fisher-F, as appropriate.
The likelihood of neonatal complications was modeled by logistic
regression (with robust estimation of the standard errors). The
explained uncertainty for the occurrence of adverse neonatal outcomes
was calculated as the R2-Naegelkerke.
The predictive performance was determined by receiver–operating
characteristic (ROC) curve analysis. Paired ROC curves were compared by
the DeLong method (33).
Statistical analyses and graph constructions were performed using STATA
13.0 (StataCorp LT, Texas, USA) and R 3.1.2 (The R Foundation for
Statistical Computing) [package “pROC”].