Imminent abortion needs more serious attention since it remains a big problem in Indonesia considering its epidemiology, morbidity, mortality, and prognosis. In fact, some cases can still be prevented. The objective of this study was to determine pathogenesis, diagnosis, and prognosis of imminent abortion through the role of antioxidant vitamin C in the interaction of superoxide dismutase (SOD), interferon-γ (IFN-γ), interleukin-4 (IL-4), vascular cells adhesion molecule-1 (VCAM-1), and decidual spiral artery resistance index (DSA RI). This study took 10 months from March to December 2007 at Obstetrics and Gynecology Department of Medical Faculty of Padjadjaran University/Hasan Sadikin Hospital, Bandung. Sixty pregnant women who met the inclusion and exclusion criteria were divided into two groups with the random clinical trial method, double-blind with repeated measurements. Data were analyzed statistically using t test, Mann-Whitney, Rank Spearman, Wilcoxon, t paired, and diagnostic test. The results of this study showed that the incidence of abortion in vitamin C group was 9 cases (30%) and placebo group was 13 cases (43.3%).