Value of amniotic fluid neutrophil collagenase concentrations in preterm premature rupture of membranes

OBJECTIVE: Neutrophils in amniotic fluid are thought to be of fetal origin, and therefore the detection of these cells and/or their products in amniotic fluid may reflect the fetal inflammatory status. We propose that amniotic fluid neutrophil collagenase (matrix metalloproteinase-8) is a useful parameter to predict adverse neonatal outcome, impending preterm labor/delivery, and intrauterine infection in the setting of preterm premature rupture of the membranes. STUDY DESIGN: Amniotic fluid was obtained by transabdominal amniocentesis from 101 patients with preterm premature rupture of the membranes (gestational age, 24-36 weeks). Fluid was cultured for aerobic and anaerobic bacteria and Mycoplasmas. Amniotic fluid analysis included Gram stain, white blood cell count, and determination of interleukin-6 and matrix metalloproteinase-8 concentrations (enzyme-linked immunosorbent assay). RESULTS: Neonates with adverse neonatal outcome were born to mothers with a significantly higher median amniotic fluid matrix metalloproteinase-8 concentration than those without adverse neonatal outcome (median, 54.4 ng/mL; range, 0.82-14,500 ng/mL vs median, 28.9 ng/mL; range, 0.78-2451.8 ng/mL; P < .05, respectively). The higher the amniotic fluid matrix metalloproteinase-8 concentrations, the shorter the interval to delivery (Cox proportional hazards model adjusting for gestational age at delivery; hazard ratio, 1.9; 95% Cl, 1.1-3.5; P < .03). Amniotic fluid matrix metalloproteinase-8 concentration was more sensitive than an amniotic fluid white blood cell count and interleukin-6 in the detection of microbiologically proven intra-amniotic infection. CONCLUSION: Increased concentrations of neutrophil collagenase (matrix metalloproteinase-8) in amniotic fluid are associated with intra-amniotic infection, impending preterm delivery, and adverse neonatal outcome in patients with preterm premature rupture of the membranes. Moreover, matrix metalloproteinase-8 in amniotic fluid is a stronger predictor for the duration of pregnancy and intra-amniotic inflammation than interleukin-6 and an amniotic fluid white blood cell count.