Background: Matrix metalloproteinase-9 (MMP-9) is the most active MMPs in the fetomaternal membranes. It plays an important role in the breakdown and remodeling of these membranes. Thus, increased knowledge of its expression in cases of premature rupture of membranes (PROM) with and without chorioamnionitis (CA) is essential for developing effective treatment strategies. Patients and Methods: expression of MMP-9 in fetomaternal membranes and maternal serum were performed in 70 full-term pregnant women; 20 cases were with intact membranes (group I), 35 with PROM (group IIA) and 15 with PROM and CA (group IIB). Results: A significant difference in MMMP-9 expression was detected between the studied groups. The highest MMP-9 expression was reached in women with PROM accompanied by histological (subclinical) CA followed by women with PROM without CA, compared to the control group (with intact membranes) at the time of delivery. Immunohistochemical expression was associated with a concomitant increase in serum MMP-9. Conclusion: MMP-9 could predict women liable for premature rupture of membranes, and the determination of its serum level may be an effective tool for PROM detection.