The fetal inflammatory response syndrome is a multisystem disorder associated with impending preterm delivery and adverse neonatal outcome. Inflammation of the umbilical cord--funisitis--is the histologic counterpart of fetal inflammatory response syndrome and has been associated with an increased risk for the development of cerebral palsy. Neutrophils found in the amniotic cavity are of fetal origin. Therefore, neutrophil secretory products may be an index of the fetal inflammatory response syndrome. To test this hypothesis, we examined the relationship between levels of amniotic fluid matrix metalloproteinase-8 and funisitis.The relationship between the presence of funisitis and concentrations of amniotic fluid matrix metalloproteinase-8 was examined in 255 consecutive patients who delivered preterm singleton neonates (gestational age, <36 weeks) within 72 hours of amniocentesis. Amniotic fluid was cultured for aerobic and anaerobic bacteria and for mycoplasmas. Funisitis was diagnosed in the presence of neutrophil infiltration into the umbilical vessel walls or Wharton jelly. Matrix metalloproteinase-8 was measured by use of a specific immunoassay. Nonparametric statistics were used for analysis.Funisitis was present in 23% (59/255) of cases. Patients with funisitis had a significantly higher median concentration of amniotic fluid matrix metalloproteinase-8 than those without funisitis (median, 433.7 ng/mL [range, 1.5-3836.8 ng/mL] vs median, 1.9 ng/mL [range, <0.3-4202.7 ng/mL]; P <.001). The diagnostic indices of matrix metalloproteinase-8 (cutoff, 23 ng/mL) in the identification of funisitis were: sensitivity of 90% (53/59), specificity of 78% (153/196), positive predictive value of 55% (53/96), and negative predictive value of 96% (153/159).There is a strong association between increased levels of amniotic fluid matrix metalloproteinase-8 and funisitis. We propose that determination of amniotic fluid matrix metalloproteinase-8 concentrations may assist the assessment of the fetal inflammatory status, thereby eliminating the need for fetal blood sampling.