Primary Splenic Pregnancy: A Systematic Review of Published Case Reports

Background/Objectives: Primary splenic pregnancy (PSP) is a rare and life-threatening form of extrauterine pregnancy. Evidence is limited to case reports, and detailed analyses of all aspects of PSP are lacking. The objective is to review and summarize the clinical features, diagnostic methods, management strategies, and maternal outcomes of PSP. Methods: Review followed PRISMA 2020 guidelines. We conducted a literature search to identify all published reports of PSP in PubMed, PubMed Central, and Google Scholar published until September 2025. The search items included: 'splenic pregnancy', 'splenic ectopic pregnancy', 'ectopic pregnancy', 'pregnancy', and 'spleen'. Additional studies were identified by reviewing the reference lists of retrieved studies. We included all available full-text cases, with the inclusion criterion being PSP and the exclusion criterion being secondary splenic pregnancy. The data on clinical presentation, diagnostics, management, and outcomes were extracted and summarized descriptively. Results: Sixty published cases of PSP were collected. The average maternal age was 30.3 years, and most cases were reported in Asia. No consistent pattern of potential risk factors was observed; cases occurred between 4 and 14 weeks of gestation. Abdominal pain was the most common symptom (86.7%), often localized to the left upper quadrant. Hypotension and hemoperitoneum were present in 41.7% and 60.0% of cases, respectively. Ultrasound was the most used initial imaging modality, whereas CT and MRI showed high concordance with the final diagnosis. Most implantations occurred on the inferior and superior poles of the spleen. Surgical intervention was the predominant approach (90%), primarily involving laparotomy with splenectomy or partial splenectomy. Antibiotic use was rarely documented. Medical management was reported in selected cases, but no βhCG threshold for PSP can be inferred. Maternal survival was almost universal; the single reported death occurred in the earliest case. Conclusions: PSP should be excluded when left-sided abdominal pain, particularly with intra-abdominal bleeding, accompanies an empty uterus and elevated βhCG. No reliable βhCG threshold for treatment selection has been established, and management should be individualized based on clinical condition, diagnostic imaging, and available expertise, based on low level of evidence. Although maternal survival is excellent, spleen-preserving and non-surgical approaches remain rare.