the study period. The current study included only women
who had their first delivery during 2006 and their subse-
quent delivery between 2007 and 2010 (n = 127,723). The
diagnostic criteria for preeclampsia used in Korea are
blood pressure ≥ 140/90 after 20 weeks’ gestation com-
bined with proteinuria (≥0.3 g/24 hr or ≥ +1 on a urine
dipstick; ICD-10 code O14). To identify the risk factors
for preeclampsia, data of the women’s characteristics such
as age, multiple pregnancies (defined as twin or higher-
order gestation), delivery mode (vaginal delivery or
cesarean section), and time interval between the first and
second pregnancy were obtained.