Statistical analysis
Continuous variables were expressed as median (25% percentile, 75%
percentile) and compared with Mann-Whitney U test; categorical variables
were expressed as number (constituent ratio) and compared with χ² test,
continuity correction χ² test or Fisher’s exact test between pregnant
and none-pregnant groups. A two-sided α of less than 0.05 was considered
statistically significant. Statistical analyses were done using the SAS
software, version 9.4, unless otherwise indicated.