ABSTRACT Objective: The aim of this study was to investigate whether the neutrophil/lymphocyte ratio (NLR) and the platelet/lymphocyte ratio (PLR) have an effect on birthweight, gestational age and the severity of prematurity. Design: Retrospective cohort study Setting: Kayseri Education and Research Hospital Methods: The data of 15000 women who delivered at the Kayseri Training and Research Hospital between May 2018 and December 2019 were retrospectively scanned. The complete blood count (CBC) values taken from the patients at least 1 month before the birth were used in the study. Main Outcome Measures: Primary outcome was to evaulate the effect of NLR and PLR on prematurity severity, birthweight and gestational week. Results: A total of 637 patients were included in the study. The gestational age at birth was determined to be associated with an increase in maternal Hb value and a decrease in PLR. A decrease in Hb, PLR, and neutrophil count, and an increase in BMI and NLR were each determined to be independent factors for birthweight. Conclusion: This is the first study to have investigated the effect of PLR and NLR on the severity of prematurity. While no correlation was determined between the severity of prematurity and NLR, there was seen to be a weak positive correlation with PLR. Key Words: neutrophil/lymphocyte ratio, platelet/lymphocyte ratio, prematurity, inflammation, birthweight Funding: None