Background: Premature rupture of membrane (PROM) is the rupture of fetal membranes at least 1 hour before the onset of labor pain. In this study, we sought to determine the predictive value of maternal serum level of procalcitonin (PCT) in the early diagnosis of chorioamnionitis in women with preterm PROM (PPROM). Methods: In this prospective cohort study, owing to limited financial resources, 48 patients with PPROM in the Kosar Ward of Motahari Hospital in Urmia, Iran were selected to comprise the sample. Inclusion criteria were amniotic fluid leak, positive ferning and nitrazine tests, gestational age 28-33 weeks, and lack of fetal tachycardia. Exclusion criteria were chronic and congenital heart disease and use of non-steroidal antiinflammatory drugs. Data were analyzed using SPSS v. 19 software; descriptive statistics, independent t-tests, and the Pearson test were also performed. Results: We studied 48 pregnant women and their neonates. Approximately 40% of women had chorioamnionitis; approximately 60% of women did not have chorioamnionitis. Moreover, approximately 69% of the neonates had a 5-minute Apgar score ≥7. A significant correlation was observed between women who had histopathology confirmed chorioamnionitis and neonate hospitalization in the neonatal intensive care unit (P<0.001). The sensitivity, specificity, and positive and negative predictive values of PCT inflammatory indices were 100%, 79%, 57.5%, and 100%, respectively, for the histopathologic diagnosis of chorioamnionitis. Conclusion: In pregnant women, we found a significant correlation between PCT index at delivery and histopathologic chorioamnionitis.