Aspirin improves uterine blood flow in the peri-implantation period.

A prospective clinical study at the Infertility Clinic of National Cheng Kung University Hospital investigated the effect of aspirin on infertile women with impaired uterine perfusion. A total of 127 women with unexplained infertility or repeated failure with various assisted-conception techniques were enrolled. Uterine perfusion was assessed by Doppler ultrasound and classified as normal or impaired (pulsatility index < 3.0 or > or = 3.0, respectively). One-third (43/127) of the women were found to have impaired uterine perfusion during their menstrual cycles. Those with impaired uterine blood flow were given aspirin (100 mg/day) starting on day 3 of the next ovulatory cycle. Only 36 women completed both the screening and the aspirin-treated cycles. The pulsatility index was measured in the natural and aspirin-treated cycles in the same group of women and compared using repeated measures analyses of variance. A significant improvement in the uterine blood perfusion (p < 0.05) was detected on the day leutinizing hormone peaked and in the midluteal phase (peri-implantation period) of aspirin-treated cycles. Thus, the use of low-dose aspirin may improve uterine perfusion in women with unexplained infertility and impaired uterine blood flow.