A prospective observational study was performed. 60 pregnant women in their 19th_ 24th week of gestation ., This study showed that maternal serum soluble endoglin level in the second trimester of pregnancy was significantly higher in women who developed preeclampsia than who didn't develop preeclampsia (13.09 ±2.88 ng/mL vs. 5.83 ±0.81ng/mL, p<0.01).Furthermore our study revealed that there were significant differences in values of serum soluble endoglin level in cases of mild and severe preeclampsia (12.03 ±1.7 ng/mL vs. 17.87 ±2.11 ng/mL, p<0.01).Also it was demonstrated that cut-off values of 8.35ng/mL and 15.25ng/mL optimally identified patients with risk to develop preeclampsia and severe preeclampsia respectively.These results indicate the predictive value of serum soluble endoglin level as a laboratory marker of preeclampsia and its severity.