Abstract: Matrix metalloproteinases (MMPs) are zinc proteinases that degrade compounds of the extracellular matrix (ECM), which are inhibited by their natural inhibitors, tissue inhibitors of matrix metalloproteinases (TIMPs). MMPs involve in many processes of tissue remolding through degrade ECM. A successful pregnancy depends on trophoblastic invasion of endometrial and implant embryo into uterus, through invasive vascular endothelial to make the vascular remodeling and meet the placental blood supply. MMP-9 plays an important role in trophoblast invasion, placental vascular remodeling and delivery through playing protease function and degrading ECM. The imbalance between MMP-9 and its inhibitor TIMP-1 relates to many pathological pregnancy processes, such as spontaneous abortion, preterm labour, hypertensive disorder complicating pregnancy and gestational diabetes mellitus. This article summarizes the role of MMP-9 in normal pregnancy and pathologic pregnancy. The current knowledge in the field of identified ECM proteases will be contributive to the innovative therapeutic intervention in pathological pregnancy processes.

Key words: Matrix metalloproteinase 9, Embryo implantation, Pregnancy, Pregnancy complications, Vascular remodeling