Background and Objective: In the past three decades, the efficacy of using low dose aspirin for preeclampsia prevention has been an important matter in obstetrics research. The purpose of this study was to determine the effectiveness of aspirin in the prevention of preeclampsia in high risk women with abnormal uterine artery Doppler ultrasonography findings.

Materials and Methods: This randomized double blind clinical trial was done in Kowsar hospital in Qazvin, Iran in 2015. All singleton pregnant women at 11-14 weeks of gestation were evaluated by uterine artery Doppler ultrasound and in the case of abnormal findings, were divided into two groups of case (n=50) and control (n=50). The case group received aspirin 80 mg/day and the control group received daily placebos. Both groups were followed up until delivery and pregnancy outcomes including incidence of preeclampsia, intrauterine growth restriction, preterm labor, mode of delivery, 1st and 5^th min Apgar score and neonatal birth weight were recorded. All these data were analyzed with T-Test and Chi-square statistical methods.

Results: Preeclampsia occurred in 6 individuals (12%) in the case group and 12 individuals (24%) in the control group, however this reduction was not statistically significant (P=0.3). No significant difference was observed between the two groups in fetal growth restriction, preterm labor, mode of delivery and Apgar score. Average birth weight in the case group was slightly higher than the control group (P=0.05).

Conclusion: The findings of this study demonstrated that the administration of aspirin from 14 weeks of gestation to women with abnormal Doppler ultrasonography findings could not reduce the risk of preeclampsia.