Statistical analysis
We used Microsoft Excel and R for Windows version 4.1.1.(32). Descriptive statistics (i.e., frequencies and percentages for categorical data) were used and no data were imputed as missing data was negligible (<5%). Trends over time in mode of birth and perinatal outcomes were depicted in graphs. For all perinatal outcomes we excluded the cases with stillbirth or unknown moment of death.
Since our data are population-based rather than a sample that requires extrapolation we present our data as absolutes and percentages without statistical analysis.