Spontaneous abortion is the most common complication of pregnancy and responsible for significant emotional distress to couples desiring children. Approximately 70% of human conceptions fail to achieve viability and an estimated 50% are lost before the first missed period. More than 80 percent of abortions occur in the first 12 weeks of pregnancy, and the rate decreases rapidly thereafter (Harlap et al., 1980). The aim of this work was to study the transvaginal color Doppler uterine artery resistive index and Corpus luteum vessels resistive index in combination with serum progesterone and ك-HCG levels in first trimesteric threatened abortion patients.