Student’s t test was used to compare continuous vari-
ables between groups, while the chi-square test was used
to compare categorical variables. To evaluate the risk of
preeclampsia in the second pregnancy, a model of multi-
variate logistic regression analysis was performed with
preeclampsia as the final outcome among the entire
study population. We then conducted a sub-analysis
stratified by preeclampsia status in the first pregnancy.
A P value < .05 was considered statistically significant.
Statistical analyses were performed using SPSS software,
version 12.0 (SPSS Inc, Chicago, IL, USA).