OBJECTIVE: Preeclampsia is one of the most serious problems that can occur in pregnancy. This study focused on the effect of A disintegrin and metalloproteinase containing type 1 thrombospondin motifs 1 (ADAMTS-1) and ADAMTS-4 immunoreactivity between placentas from women with preeclampsia and normotensive healthy women at the third trimester of pregnancy. STUDY DESIGN: Sixty placentas (60 samples) from women with preeclampsia and normotensive healthy women in pregnancy at weeks 29-35 were included in this study. Clinical parameters and the presence of decidual cells and chorionic villus in the placenta samples were compared with women with preeclampsia and normotensive healthy women. RESULTS: The p value was found to be significant according to expression of ADAMTS-1 and ADAMTS-4 (p<0.001). Hypertrophy in cytotrophoblast cells, dilation and congestion in blood vessels in the stromal region, the accumulation of perivillous fibrin degeneration nuclei in decidual cells, pyknosis, and apoptotic changes were observed in the placentas from preeclampsia group. The expression levels of ADAMTS-1 and ADAMTS-4 were found to be significantly lower in placentas from women with preeclampsia than in normotensive healthy women. CONCLUSION: Decrease in ADAMTS-1 and ADAMTS-4 expression may be a key in regulating placental morphology and function by affecting trophoblastic invasion, extracellular matrix development, and angiogenesis in the maternal and fetal region. © Science Printers and Publishers, Inc.