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Objective: To determine the prevalence of histological chorioamnionitis associated with preterm prelabour rupture of membranes (PPROM) in women following spontaneous onset of labour, urgent delivery or planned delivery after 34 weeks' gestation., Methods: Charts of all women admitted to Kingston General Hospital with PPROM prior to 34 weeks' gestation over five years were collected. Obstetrical outcomes and histopathology reports were reviewed., Results: Two hundred forty-four women with PPROM were identified and reviewed. The majority of women (169; 69%) went into spontaneous labour and, of those, 24 (14%) had clinical chorioamnionitis and 79 (47%) had histological chorioamnionitis. Of the 45 women (18%) who required urgent delivery, 27 (60%) had clinical chorioamnionitis and 31 (69%) had histological chorioamnionitis. Only 26 of the original 244 women with PPROM (11%) were managed expectantly until 34 weeks' gestation and then had a planned delivery. The prevalence of histological chorioamnionitis in this group whose placentas were sent for histopathologic review was 24%. Overall, the clinical suspicion of chorioamnionitis was found to be specific (91%) but not sensitive (37%) for identifying chorioamnionitis on the basis of histopathology., Conclusion: Histological chorioamnionitis complicates almost one half of all cases of PPROM that occur prior to 34 weeks' gestation. Most women will progress to spontaneous labour or require urgent delivery for clinical chorioamnionitis or other complications related to ruptured membranes before reaching 34 weeks' gestation. Only a subset of women remain pregnant long enough to have labour induced, but among those the prevalence of histological chorioamnionitis is lower (24%).