The benefits of low-dose aspirin therapy in women with impaired uterine perfusion during assisted conception.

The objective of this long-running study was to determine whether the addition of low-dose aspirin to a standard hormone replacement therapy (HRT) protocol improved uterine perfusion during assisted conception. A total of 99 women scheduled for frozen embryo replacement were studied. Endometrial preparation was with a standard buserelin/HRT protocol. Uterine perfusion was assessed by Doppler ultrasound and classified as impaired or normal. In their first attempts, those with impaired perfusion (group I, n = 37) received low doses of aspirin [150 mg (n = 26) or 300 mg daily (n = 11)], starting from day 13 of HRT. Women with normal perfusion (group II) did not receive aspirin. In subsequent attempts, those from group I were arbitrarily allocated to start aspirin on day 1 or day 13 of HRT, and 10 women from group II were arbitrarily selected to receive aspirin from day 1 of HRT. In group I, the cancellation (46 versus 36%) and pregnancy rates (15 versus 25%) in those who received 150 or 300 mg aspirin daily were similar. In those with cancelled first attempts, good perfusion was achieved in 82 versus 20% (P < 0.02) of subsequent attempts using aspirin from day 1 versus day 13 of HRT. Higher pregnancy rates (47 versus 17%) were achieved in those taking aspirin from day 1 of HRT. In group II, pregnancy rates were not statistically different in those who did or did not receive aspirin during their subsequent attempts (10 versus 35%). The addition of low-dose aspirin to a standard HRT protocol in women with impaired uterine perfusion is associated with improved blood flow and satisfactory pregnancy rates.