ABSTRACTBackground: Preeclampsia is a syndrome of unknown etiology characterized by hypertension, proteinuria, and/or organ dysfunction. CA125 is an antigenic determinant recognized by the murine monoclonal antibody OC125 quantified by radioimmunoassay. Its role in obstetrics is yet to be fully understood as most clinical trials advocating its uses are widely experimental in nature and unacknowledged. Aim: This study was done to assess the relationship between serum concentration of CA125 in normal pregnancies and those complicated with preeclampsia. Methods: A case–control study involving 70 women diagnosed with preeclampsia and 70 healthy controls matched for age, parity, and gestational age at enrollment. Venous samples were collected from each participant after informed consent was obtained. The preeclampsia group was further subdivided into mild and severe preeclampsia and all participants were followed up till delivery with records of delivery, maternal, and neonatal outcomes obtained thereafter. Serum CA125 levels were determined by standard enzyme-linked immunosorbent assay (ELISA) method. Hypothesis testing was done using chi-square test for categorical variables, and the independent-samples t-test and ANOVA for numerical variables. All significances were reported at P < 0.05. Results: The mean serum level of CA125 in women with preeclampsia was significantly greater than those with normal pregnancy (54.17 IU/mL vs. 12.49 IU/mL, P < 0.05). CA125 level also correlated positively with systolic blood pressure (r = 0.406, P < 0.05), diastolic blood pressure (r = 0.433, P < 0.05), serum uric acid levels (r = 0.407, P = 0.001), platelet levels (r = 0.341, P = 0.001), and urinary protein levels (r = 0.325, P = 0.002). The CA125 levels between the three categories of participants in the study were: normotensive control (12.49 ± 6.62 mIU/L), mild preeclampsia (29.43 ± 3.7 mIU/L), and severe preeclampsia (64.25 ± 9.21 mIU/L), respectively (P = 0.023). Conclusion: We can infer from this study that increased maternal serum CA 125 levels are associated with the preeclampsia and its severity. However, further validation of these findings with more robust multicenter prospective and longitudinal characterization of maternal serum CA125 profiles in pregnancy should be carried out in subsequent investigations to determine its suitability as a predictive biomarker for preeclampsia in women of African descent.