Maternal sepsis continues to be a maternal health problem associated with 75,000 deaths per year worldwide, representing a greater burden in low- and middle-income countries (LMICs). Although the Shock Index (SI) has been widely studied in postpartum hemorrhage and in non-obstetric populations, it has not yet been widely studied in sepsis. We aimed to identify the relationship between Shock Index and suspected sepsis in pregnant and postpartum patients to explore the use of Shock index in the context of maternal sepsis and its relationship with sepsis-related outcomes. A single-center, retrospective, case-control study was conducted, including pregnant and postpartum patients attended between June 2015 and December 2020 in a high-complexity university hospital. This study was conducted in a High Obstetric Complexity Unit (UACO) in the southwest region of Colombia. Pregnant or postpartum women with infectious processes of obstetric or non-obstetric origins were included. Cases had sepsis diagnosis; controls showed infection process and systemic inflammatory response signs without confirmed sepsis. Those with unconfirmed infections and preterm conditions were excluded. A logistic regression model was conducted to examine the association between maternal factors and sepsis diagnosis, and significant variables were determined through univariate analysis and included in a multivariate model. A total of 640 patients were included (343 cases and 297 controls), sepsis was significantly associated with a higher shock index at admission SI ≥ 0.9 (85.4% vs 75%, p = 0.001). No correlation was found between the Shock Index and C-reactive protein (CRP), leukocyte count, or ICU length of stay. The area under the receiver operating characteristic curve (AUROC) analysis identified a Shock Index of 1 as the optimal cutoff point, while the cutoff point of 0.9 demonstrated the highest sensitivity (85%). An SI ≥ 0.9 increased the risk of sepsis 1.94 times (95% CI 1.31-2.91, p = 0.001) and remained significant in the adjustment model (OR_adj 2.18, 95% CI 1.42-3,32, p < 0.001). Incidence of maternal sepsis, incidence of maternal complications, and perinatal outcomes were measured with a SI ≥ 0.9. Our findings underscore the importance of using the Shock Index with a cutoff point of 0.9 as a predictive tool for sepsis in pregnant patients, emphasizing the need for timely intervention and continuous monitoring of patients.