Non-invasive prediction of chorioamnionitis in women with preterm premature rupture of membranes

Abstract

Introduction: The purpose of this study was to develop a model based on non-invasive clinical and ultrasonographic parameters to predict the occurrence of subsequent chorioamnionitis in pregnant women with preterm premature rupture of membranes (PPROM). Additionally, this investigation was conducted to determine if additional invasive test results improve the prediction of occurrence of subsequent chorioamnionitis from the non-invasive model. Methods: Transvaginal ultrasonographic assessment of cervical length was performed. Maternal serum C-reactive protein (CRP) and white blood cell (WBC) counts were also measured immediately after amniocentesis in 146 consecutive women with PPROM at 20+0 and 33+6 weeks of gestation. Amniotic fluid (AF) obtained by amniocentesis was cultured, and interleukin-6 (IL-6) levels and WBC counts were determined. Outcome measures were histologic or clinical chorioamnionitis. The placentas were examined histologically for the presence of chorioamnionitis and the pregnant women were evaluated for evidence of clinical chorioamnionitis. Results: The prevalence of histological and clinical chorioamnionitis was 50.7% (74/146) and 8.9% (13/146), respectively. A risk score based on a non-invasive model (model 1), including serum CRP and gestational age, was calculated for each patient. The model was shown to have an adequate goodness of fit, and the area under the receiver operating characteristic curve (AUC) was 0.742. When including AF tests results (e.g., AF IL-6 levels) as invasive markers in the non-invasive model, serum CRP was excluded from the final model (model 2) as insignificant, whereas AF IL-6 and gestational age remained in model 2. No significant difference in AUC was found between models 1 and 2. For the outcome of clinical chorioamnionitis, none of the parameters studied could be used to identify pregnant women at high risk for the development of clinical chorioamnionitis. Conclusions: For pregnant women with PPROM, the non-invasive model based on serum CRP and gestational age was shown to be moderately predictive of histologic chorioamnionitis development. However, invasive test results did not add predictive information to the non-invasive model in this setting.