Objective To analyze the relationship between periodontal condition and premature rupture of membrane（PROM） in order to provide basis to keep pregnant women from oral diseases. Methods 18 cases of preterm pregnant women with PROM（Group PPROM）and 20 cases of full term pregnant women with PROM（Group PROM）were selected as the study group, and 28 cases of full term normal pregnant women were selected as the control group. Everyone’s plaque index（PLI）, probing depth（PD） and sulcular bleeding index（SBI） were checked and recorded. Meanwhile, immunohistochemical method was used to detect the distribution and expression of matrix metalloproteinase-9 （MMP -9） in fetal membrane of cervix. The relationship between the expression of MMP -9 and PROM was analyzed. Results The expression of MMP-9 in the pregnant women with PROM（Group PPROM and Group PROM） was higher than that in the control group. There was no relationship between the expression of MMP-9 in chorion and PD（r=0.053, P=0.075）. The expression of MMP-9 in chorion had direct correlation with SBI（r=0.433, P
