Aim: The aim of this study was to determine midkine (MK) expression in women with preeclampsia (PE) compared with those in a normal pregnancy. Materials and Methods: This study included 45 patients with PE and 35 patients in a control group. Women with PE who had a diagnosis of preeclampsia before gestational week 34 were included in the early PE group (n = 20). Women diagnosed with PE after gestational week 34 were in the late PE group (n = 45). Serum MK levels were compared between the groups. Results: MK level was neither different between normotensive women and those with early PE nor was it different between the early and late PE groups. MK levels were significantly different between the normal pregnancy and late PE groups. The MK level decreased in the late PE group compared with that in the normal pregnancy group. Conclusion: Serum MK levels significantly decrease in late PE women compared with normally pregnant women.