Aim: The aim of this study is to retrospectively evaluate the effects of antenatal MgSO4 administration on maternal inflammatory response indicators NLR, SII, and SIRI. Materials and Methods: Between January 2021 and December 2023, 35 pregnant women who were followed up in the perinatology department of a medical faculty hospital, who were administered MgSO4 for fetal neuroprotection at ≤ 32 weeks, and whose data were obtained from the electronic record system were retrospectively examined. Baseline and post-MgSO4 leukocyte, neutrophil, lymphocyte, monocyte, and platelet values were recorded at 12 hours. NLR, SII, and SIRI calculations were performed using standard formulas. Continuous data were compared using the t-test for dependent groups, and categorical data were analyzed using the chi-square test; p < 0.05 was considered statistically significant. Results: The mean gestational age was 29.8 ± 2.2 weeks, and the mean birth weight was 1363 ± 413 g. A significant increase in leukocyte and neutrophil counts was observed after MgSO4 administration (p < 0.05), while no significant changes were detected in lymphocyte, monocyte, and platelet counts (p > 0.05). NLR and SIRI increased significantly (p < 0.05), while the increase in SII was not significant (p > 0.05). Conclusion: MgSO4 administration has a variable effect on maternal inflammatory response parameters; NLR and SIRI increase, while no significant change is observed in SII. These findings should be confirmed in prospective, randomized studies with larger sample sizes.