background: Increased uterine artery (UtA) vascular impedance at the time of embryo transfer can decrease implantation and pregnancy rates in women undergoing IVF/ICSI. We hypothesized that low-dose aspirin decreases UtA vascular impedance on the day of embryo transfer in unselected IVF/ICSI patients when medication is started concomitantly with controlled ovarian stimulation. In addition, as secondary outcome measures, we investigated whether low-dose aspirin decreases the incidence of

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... mal (bilateral UtA PI ! 3.0) uterine haemodynamics and whether it affects arcuate, radial and spiral artery vascular impedances and endometrial thickness. methods: A total of 122 women who underwent IVF/ICSI were randomized to receive 100 mg aspirin (n ¼ 61) or placebo (n ¼ 61) daily, starting on the first day of gonadotrophin stimulation. Doppler ultrasonography was performed on the day of embryo transfer. results: Embryo transfer took place in 57 women in the aspirin group and in 56 women in the placebo group. UtA mean PI values did not differ significantly between the groups. The incidence of non-optimal uterine haemodynamics was lower in the aspirin group than in the placebo group (P ¼ 0.03). Other secondary outcome measures did not differ between the groups. conclusions: In unselected IVF/ICSI women, low-dose aspirin therapy, when started concomitantly with controlled ovarian stimulation, did not affect UtA vascular impedance on the day of embryo transfer. However, the incidence of non-optimal uterine haemodynamics was significantly lower in the aspirin group than in the placebo group. ClinicalTrials.gov: NCT00683202.