Statistical analyses
Distribution of data was analysed using the Kolmogorov-Smirnov test.
Normally distributed data are expressed as mean ± standard deviation.
Not normally distributed variables are expressed as median and
minimum-maximum. Categorical data are given as counts (n) and
percentages (%). Continuous data were compared with paired t-test and
Wilcoxon signed-rank test, respectively. Categorical data were compared
with Chi2 and Fisher’s Exact test, respectively, with
a 99% Confidence Interval (CI). Nonparametric receiver operating
characteristics (ROC) analysis was performed to predict the prognostic
power of the risk score and to generate a cut-off value that
discriminated best between the event of stillbirth versus live birth.
Odds ratio (OR), as measure of the relative risk of stillbirth, was
estimated using logistic regression analyses with a 95% CI. All
reported p -values are two-sided, and level of significance was
set at <0.05. Statistical tests were performed and figures
created by SPSS® Statistics Version 26.0.0.0 (IBM Corporation ©, Armonk,
NY, USA).
The study was approved by the Ethics Committee of the Medical University
of Vienna (EK 1759/2018 ) and complied with the principles
outlined in the Helsinki Declaration of 1975, as revised in 2013.
Patients’ written consent was not required as per Austrian Federal
Act concerning Protection of Personal Data (DSG 2000).