Maternal Sepsis: The Immunological Complexity Behind Delayed Recognition

Sepsis has long remained one of the leading causes of avoidable mortality worldwide, contributing to an estimated 1 in 5 deaths (1). Maternal sepsis, defined as life-threatening organ dysfunction resulting from infection during pregnancy, childbirth, post-abortion, or the postpartum period, presents a particular clinical challenge due to the difficulty of early recognition during pregnancy and postpartum recovery. According to the World Health Organization, infections and sepsis remain one of the major contributors to pregnancy-related deaths, with the greatest burden falling on low- and middle-income countries (2).

What makes maternal sepsis particularly dangerous is not only its rapid progression, but the difficulty of early identification. Pregnancy is accompanied by profound physiological and immunological adaptation designed to protect both mother and fetus. Yet these same adaptations can obscure the early signs of systemic infection, delaying diagnosis at a time when every hour matters (3). Improving understanding of immune dysregulation in pregnancy is therefore essential to safeguarding maternal health worldwide.

Pregnancy and the Immune System: A Delicate Balance

Pregnancy requires a highly coordinated immune response, with the maternal immune system undergoing dynamic modulation to tolerate the developing fetus while still maintaining protection against pathogens (4). This balance involves shifts in cytokine signaling, changes in immune cell populations, and alterations in inflammatory responses throughout gestation.

While these adaptations are necessary for a healthy pregnancy, they can also complicate infection recognition. Physiological changes such as increased heart rate, elevated respiratory rate, and mild leukocytosis can mimic the early signs of sepsis, making diagnosis more challenging. Inflammatory markers can also fluctuate during pregnancy and the postpartum period, reducing the reliability of conventional indicators of infection (5).

From Infection to Systemic Inflammation

Postpartum endometritis, urinary tract infections, pneumonia, and surgical site infections following caesarean delivery are just some of the infections which can lead to maternal sepsis. If these localized infections are not rapidly controlled, dysregulated immune activation can trigger widespread systemic inflammation (2).

Pro-inflammatory cytokines including IL-6, TNF-α, and IL-1β play central roles in this response. Excessive cytokine release contributes to endothelial dysfunction, increased vascular permeability, and activation of coagulation pathways (6). As inflammation escalates, tissue perfusion may become impaired, leading to organ dysfunction and, in severe cases, septic shock.

At the same time, the immune response may shift toward a compensatory anti-inflammatory state intended to limit tissue damage (6). However, excessive immune suppression can leave patients vulnerable to secondary infections and poorer outcomes. This complex and rapidly evolving immune landscape makes maternal sepsis particularly difficult to predict and manage clinically.

The Diagnostic Challenge

Early diagnosis remains one of the most important factors in improving outcomes and reducing maternal sepsis mortality. Symptoms including fever, tachycardia, fatigue, and abdominal pain may initially appear non-specific or overlap with normal postpartum recovery. Blood cultures, while important, may take time
and can fail to identify the causative pathogen in some cases (7).

As a result, increasing attention has turned toward host-response biomarkers that may support earlier detection and risk stratification. Biomarkers such as C-reactive protein (CRP), procalcitonin, and inflammatory cytokines have been widely investigated, although interpretation remains challenging due to the physiological immune changes associated with pregnancy (5).

Emerging research is also exploring multi-biomarker approaches, combining inflammatory, endothelial, and coagulation-associated markers with the aim of improving diagnostic accuracy (8). Advances in immunoassay technologies and immune profiling may ultimately support faster, more precise identification of maternal sepsis before severe organ dysfunction develops.

Awareness, Research, and Early Intervention

Many maternal deaths from sepsis could be avoided through early recognition, clean birthing practices, and prompt antibiotic treatment, but despite this, it continues to be a major cause of death for pregnant women (9). Delayed diagnosis, limited healthcare infrastructure, and the growing threat of antimicrobial resistance further compound the challenge, particularly for women in resource-limited settings.

Improving outcomes will require continued investment in maternal healthcare, greater awareness of sepsis symptoms during and after pregnancy, and ongoing research into the immunological mechanisms that drive disease progression. Meanwhile, the continued global impact of maternal sepsis serves as a reminder that advancing early detection and improving our understanding of immune dysregulation in pregnancy remain critical to protecting maternal health worldwide.

1. Sepsis Facts. (n.d.). World Sepsis Day – September 13. https://www.worldsepsisday.org/sepsisfacts
2. Cao, J., Xue, D., Gao, D., & Zhang, G. (2025). Maternal sepsis and other maternal infections: Global Burden from 1990 to 2021. BMC pregnancy and childbirth, 25(1), 612. https://doi.org/10.1186/s12884-025-07722-w
3. Bauer, M. E., Perez, S. L., Main, E. K., Norman, G. S., Fish, L. J., Caldwell, M. A., Allen, C., Hughes, B. L., Gibbs, R. S., & Smith, K. L. (2024). Near-miss and maternal sepsis mortality: A qualitative study of survivors and support persons. European journal of obstetrics, gynecology, and reproductive biology, 299, 136–142. https://doi.org/10.1016/j.ejogrb.2024.05.038
4. Abu-Raya, B., Michalski, C., Sadarangani, M., & Lavoie, P. M. (2020). Maternal Immunological Adaptation During Normal Pregnancy. Frontiers in immunology, 11, 575197. https://doi.org/10.3389/fimmu.2020.575197
5. Mertens, K., Muys, J., & Jacquemyn, Y. (2019). Postpartum C-Reactive Protein: A limited value to detect infection or inflammation. Facts, views & vision in ObGyn, 11(3), 243–250.
6. Wiersinga, W. J., & van der Poll, T. (2022). Immunopathophysiology of human sepsis. EBioMedicine, 86, 104363. https://doi.org/10.1016/j.ebiom.2022.104363
7. Singer, M., Deutschman, C. S., Seymour, C. W., Shankar-Hari, M., Annane, D., Bauer, M., Bellomo, R., Bernard, G. R., Chiche, J. D., Coopersmith, C. M., Hotchkiss, R. S., Levy, M. M., Marshall, J. C., Martin, G. S., Opal, S. M., Rubenfeld, G. D., van der Poll, T., Vincent, J. L., & Angus, D. C. (2016). The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA, 315(8), 801–810. https://doi.org/10.1001/jama.2016.0287
8. Chen, L., Zhang, X., & Shi, P. (2025). Recent advances in biomarkers for detection and diagnosis of sepsis and organ dysfunction: a comprehensive review. European journal of medical research, 30(1), 1081. https://doi.org/10.1186/s40001-025-03324-6
9. World Health Organization: WHO. (2020, August 25). Sepsis. https://www.who.int/health-topics/sepsis/#tab=tab_1