The Effects of Nitric Oxide Donors on Uterine Artery and Sub-endometrial Blood Flow in Patients with Unexplained Recurrent Abortion

Background: Nitric oxide plays a major role in increasing uterine blood flow during the luteal phase and early pregnancy. This study was done to compare uterine artery and sub-endometrial blood flow indices during the luteal phase between patients with unexplained recurrent abortion and fertile women and also to evaluate the ef- fects of nitric oxide donors on blood flow indices in the abortion group. Methods: The study included a control group of 30 primiparae who had normal vag- inal delivery and no history of abortion and an abortion group of 30 nulliparous women with history of two or more unexplained recurrent abortions. Transvaginal three-dimensional pulsed color Doppler ultrasound was done on days 21-23 of the cycle to measure uterine artery resistance and pulsation indices and the subendome- trial vascular, flow and vascular-flow indices. Isosorbide mononitrate 20 mg tablet was administered vaginally in the abortion group and blood flow indices were meas- ured again after two hours. The Student t-test and the paired t-test were used for analysis of results and a p-value of ≤0.05 was considered significant. Results: Patients with unexplained recurrent abortion had significantly higher uter- ine artery resistance and pulsation indices and lower sub-endometrial vascular, flow and vascular-flow index (p<0.01-0.0001). Isosorbide mononitrite significantly de- creased uterine artery and increased sub-endometrial blood flow indices (p<0.001). Conclusion: Uterine artery and sub-endometrial blood flow decreased during the lu- teal phase in patients with unexplained recurrent abortion. Nitric oxide donors in- creased blood flow and may be of a therapeutic value.