Intra-amniotic infection is associated with increased amniotic fluid concentrations of monocyte chemotactic protein-1 in patients with preterm parturition

OBJECTIVE: Chemokines induce migration and activation of inflammatory cells to the site of tissue injury and have been recently implicated in innate immune response against microorganisms such as the AIDS virus. Monocyte chemotactic protein-1 (MCP-1) is a member of the beta family of chemokines and plays a major role in the recruitment of monocytes/macrophages during the inflammatory process. The purpose of this study was to determine if there is a relationship between amniotic fluid (AF) MCP-1 concentrations and intra-amniotic infection in patients with preterm labor. STUDY DESIGN: A cohort of patients with preterm labor and intact membranes who underwent amniocentesis and delivered before 35 weeks were studied (n - 128). AF was cultured for aerobic and anaerobic bacteria as well as Mycoplasmas, AF MCP-I concentrations were determined by specific immnnoassays. Non-parametric tests, contingency tables and survival techniques were utilized in the analysis. RESULTS: AF cultures were positive in 21.9% of the patients (28/128). Patients with ( + ) AF culture had significantly higher concentrations of MCP-1 than patients with (-) AF culture (median 18.96 ng/ml [0.71-88.2] vs. median 1.95 tig/ml [0.06-81.4], respectively, p < 0.0001). When a cut-off of 2.57 ng/ml (derived from ROC curve analysis) was used, AF MCP-1 had a sensitivity of 89% and a specificity of 56% for the diagnosis of a ( + ) AF culture. Moreover, patients with an AF MCP-1 2.57 ng/ml had a shorter amniocentesis-to-delivery interval than patients with AF MCP-1 < 2.57 ng/ml (median 24 h [1-624] vs. median 168 h [1.5-1,488], respectively, p < 0.001). This effect remained significant after adjusting for other confounding variables (gestational age at admission, cervical dilatation, AF Gram stain, and AF white blood cell count). CONCLUSION: 1) MCP-1 was detectable in all samples of amniotic fluid and therefore may play a physiologic role during development; 2) intrauterine infection results in dramatic elevations of AF MCP-1 concentrations; and 3) MCP-1 identifies patients with preterm labor and intact membranes at risk for impending delivery.