Abstract Objective To determine the value of the Aggregate index of systemic inflammation (AISI) in predicting admission to neonatal intensive care unit (NICU) and chorioamnionitis. Methods The present retrospective cohort study with pregnant women who were diagnosed with preterm premature rupture of membranes (PPROM) in the Department of Perinatology, Ministry of Health Ankara City Hospital between January 1, 2021, and June 1, 2023 ( n = 357). The patients were categorized into subgroups: (1) cases with ( n = 27) or without ( n = 330) chorioamnionitis, (2) admission ( n = 182) or no admission ( n = 175) to NICU; (3) gestational age at birth <28 weeks or 28 weeks or longer; and (4) gestational age at birth <34 weeks or 34 weeks or longer. AISI values were compared between the subgroups, and cut‐off values for AISI were determined to predict adverse outcomes. Results AISI values were significantly higher in the admission to NICU group compared with the no admission to NICU group (707.0 vs 551.2) ( P < 0.05). AISI values were also significantly higher in the chorioamnionitis group compared with those without chorioamnionitis (850.3 vs 609.4) ( P < 0.05). AISI levels were significantly higher in cases delivered before 28 weeks of gestation compared with the cases delivered at 28 weeks of gestation or later (945.6 vs 604.9) ( P < 0.05), and were also significantly higher in cases delivered before 34 weeks of gestation compared with the cases delivered at 34 weeks of gestation or later (715.5 vs 550.1) ( P < 0.05). Optimal cut‐off values of AISI were found to be 626.19 (74.1% sensitivity, 52.8% specificity), 506.09 (68.9% sensitivity and, 47.7% specificity), and 555.1 (69.8% sensitivity, 48.1% specificity) in predicting NICU admission, chorioamnionitis, and delivery before 28 weeks, respectively. Conclusion The novel inflammatory marker AISI may be used in the prediction of chorioamnionitis and NICU admission in PPROM cases. Synopsis Aggregate index of systemic inflammation may be used as a novel marker in predicting high‐risk for chorioamnionitis and neonatal intensive care unit admission in women with preterm premature rupture of membranes.