Background: This case-control study aimed to evaluate the role of Cancer Antigen 125 (CA-125) in Iraqi pregnant women experiencing vaginal bleeding, with a focus on its potential as a diagnostic marker for complications during pregnancy and predictive diagnostic cancer. Methods: A total of 23 pregnant women with vaginal bleeding were enrolled in the study in January 2025. Participants were divided into two groups: 7 women with normal CA-125 levels (control group) and 17 women with elevated CA-125 levels, diagnosed by obstetricians and gynaecologists. Venous blood samples were collected and analysed for CA-125, Vitamin D, and other relevant biochemical markers using standardised laboratory techniques. Results: The mean age of participants was 25.61 ± 3.14 years, with a body mass index (BMI) of 26.83 ± 5.13 kg/m². Most women reported bleeding for less than a week (73.91%). Statistical analysis revealed a significant difference in CA-125 levels between the two groups, with the predictive group showing higher levels (67.7 ± 8.77 U/mL) compared to the non-predictive group (20.3 ± 2.54 U/mL; p < 0.001). No significant differences were found in Vitamin D levels or other biochemical parameters between the two groups. Conclusion: Elevated CA-125 levels in pregnant women with vaginal bleeding may provide valuable diagnostic insights. Further studies are warranted to explore the clinical implications of CA-125 as a biomarker in obstetric care, particularly in populations with high rates of complications.