Fetal plasma MMP-9 concentrations are elevated in preterm premature rupture of the membranes

OBJECTIVE: The objective of this study was to determine whether the concentrations of matrix metalloproteinase-9 (MMP-9) in the fetal (fetal plasma and amniotic fluid) and maternal compartments (plasma) are different in patients presenting with preterm premature rupture of membranes (PROM) than in those with preterm labor and intact membranes. STUDY DESIGN: Fetal plasma MMP-9, interleukin-1β (IL-1β), IL-6, soluble tumor necrosis factor receptors 1 (sTNF-R1) and 2 (sTNF-R2) were measured in fetuses with preterm labor and intact membranes (n = 96) and preterm PROM (n = 43). The concentrations of analytes were determined with sensitive and specific immunoassays. A P value <.05 was considered significant. RESULTS: (1) The median fetal plasma MMP-9 concentration was significantly higher in fetuses with preterm PROM than in those with preterm labor (P = .035). (2) In contrast, fetal plasma IL-1β, sTNF-R1, and sTNF-R2 were significantly higher in patients with preterm labor than in those with preterm PROM (IL-1β, P = .01; sTNF-R1, P = .003; and sTNF-R2, P = .02). (3) The median amniotic fluid concentration of MMP-9 was higher in patients with preterm PROM than in those with preterm labor (P < .001). CONCLUSION: Fetuses with preterm PROM have increased concentrations of an enzyme (MMP-9) implicated in the mechanism of membrane rupture but lower concentrations of IL-1β, sTNF-R1, and sTNF-R2 than fetuses with preterm labor and intact membranes. A role for the fetus in the genesis of preterm PROM deserves consideration.