C-reactive protein concentration in vaginal fluid as a marker for intra-amniotic inflammation/infection in preterm premature rupture of membranes.

Objective: The purpose of this study was to determine whether C-reactive protein (CRP) concentrations in vaginal fluid can identify patients with intra-amniotic inflammation/infection (IAI) and predict adverse outcome in preterm premature rupture of membranes (PROM).

Methods: The study population consisted of 121 singleton pregnant women with preterm PROM (36 weeks of gestation) who had an amniocentesis and vaginal fluid collection. A Dacron polyester-tipped applicator was soaked with vaginal fluid for 10 seconds and diluted with 1 mL buffer solution. Amniotic fluid was cultured for aerobic and anaerobic bacteria, as well as mycoplasmas. Vaginal fluid CRP and amniotic fluid matrix metalloproteinase-8 (MMP-8) were determined by specific immunoassays. IAI was defined as an amniotic fluid MMP-8 concentration >23 ng/mL and/or a positive amniotic fluid culture. Nonparametric tests and survival techniques were used for statistical analysis.

Results: Patients with IAI had a significantly higher median vaginal fluid CRP concentration than those without IAI (median (range), 7.8 (0.1-1310.1) ng/mL vs. 1.0 (0.1-319.4) ng/mL, p < 0.005). The median amniotic fluid white blood cell (WBC) count was significantly higher in patients with a vaginal fluid CRP concentration of >10 ng/mL than in those with a lower concentration (median (range), 82.5 (0-8640) cells/mm3 vs. 2 (0->1000) cells/mm3, p < 0.001). Patients with vaginal fluid CRP concentration of >10 ng/mL had a significantly shorter sampling-to-delivery interval and higher rates of preterm delivery within five days, funisitis, and histologic chorioamnionitis than did those with a vaginal fluid CRP concentration below this cut-off. A vaginal fluid CRP cut-off of 10 ng/mL had a specificity of 89% and a sensitivity of 45% in the identification of IAI.

Conclusion: An elevated CRP concentration in vaginal fluid collected by polyester-tipped applicator is a risk factor for intra-amniotic inflammation/infection and impending preterm delivery in preterm PROM.