Objective · To study the hemodynamic parameters of uterine at midluteal phase in patients with early recurrent spontaneous abortion (ERSA) and the effect of aspirin on them. Methods · Transvaginal color Doppler ultrasonography was used to measure the parameters of uterine blood flow and the endometrial thickness at midluteal phase of 271 women with ERSA (ERSA group) and 66 women without a history of recurrent spontaneous abortion (control group). Then ERSA group were administered with aspirin 50 mg/d orally for 2 months and other individualized treatment, and the effect of aspirin on parameters of uterine blood flow and the early pregnancy outcome of them were observed. Results · At midluteal phase, the endometrium was significantly thinner in ERSA group than that in control group. Pulsatility index (PI) of endometrial blood flow and mean PI (mPI), mean resistance index (mRI), and mean systolic/diastolic ratio value (mS/D) of uterine arteries were statistically significantly higher in ERSA group in comparison to control group (P<0.05). Following aspirin treatment, resistance to uterine blood flow reduced significantly in ERSA group (P=0.000), and the endometrial thickness increased in the patients with endometrial thickness less than 7 mm (P=0.000). Only 163 ERSA patients were re-examined by transvaginal color Doppler ultrasonography after aspirin treatment, among whom 136 women was pregnant after individualized treatment. Among these pregnant patients, 97 cases were pregnant for more than or equal to 12 weeks, while 10 cases aborted during the first 12 weeks, and the early pregnancy outcomes of the other 29 cases were still unclear. Conclusion · In comparison with normal fertile women, ERSA patients have significantly higher resistance to uterine blood flow and thinner endometrium. Aspirin can improve uterine blood perfusion, which improves early pregnancy outcome.