Prediction of exact delivery time in patients with preterm labor and intact membranes at admission by amniotic fluid interleukin-8 level and preterm labor index

Aim: To examine whether delivery time for preterm labor can be predicted by clinical and biochemical markers at admission. Methods: It has previously been reported that interleukin (IL)-8 and glucose in the amniotic fluid, fetal fibronectin (fFN) in vaginal secretions and the preterm labor index (PLI) are independent risk factors for delivery before 34 weeks' gestation. Using these four markers, we developed an equation model to predict the remaining gestation period after amniocentesis by step-wise multiple regression analysis in 126 preterm delivery cases (retrospective section of the study). We also evaluated whether this equation model could predict delivery time in 65 new preterm labor patients (prospective section of the study). Finally, we investigated the risk factors for delivery within three days after amniocentesis. Results: The period from amniocentesis until delivery was calculated using the following equation by step-wise multiple regression analysis: predicted period until delivery (days) = 77.1 - 15.8 x log (amniotic IL-8 level [ng/mL]) - 9.2 x PLI (points). The calculated period until delivery correlated significantly with the actual period until delivery in the prospective study. When a high score of PLI (>= 5 points) and a high level of vaginal fFN (>= 90 ng/mL) or a high level of amniotic IL-8 (>= 25.5 ng/mL) were present, the positive predictive values were 88.2% and 80.9% in predicting delivery within three days, respectively. Conclusions: Using markers reflecting inflammation in the uterus (amniotic IL-8 or vaginal fFN) and clinical symptoms (PLI), we may be able to predict the exact delivery time in preterm labor patients with intact membranes.