Low-dose aspirin improves endometrial receptivity in the midluteal phase in unexplained recurrent pregnancy loss.

Objective: To evaluate differences in Doppler parameters and pregnancy outcomes, if any, and to determine the predictive accuracy of such indices, as well as the effects of low-dose aspirin (LDA) in unexplained recurrent pregnancy loss (URPL).

Methods: An observational study was conducted at Ren Ji Hospital, Shanghai, China, from May 2015 to December 2016. The endometrial thickness, and the pulsatility index (PI), resistive index (RI), and systolic-to-diastolic ratio (S/D) values of endometrial and uterine artery blood flow were collected. Receiver operating characteristic (ROC) curve analysis was used to analyze data from URPL patients (three or more first-trimester spontaneous abortions with unknown etiology) and patients with normal fertility. A second ultrasonography examination was performed in URPL patients who had received daily LDA for 2 months.

Results: There were 190 URPL patients and 35 control patients. Endometrial thickness was significantly thinner in URPL patients than control patients (P=0.005). The PI, RI, and S/D values for endometrial blood flow and the mean PI, RI, and S/D values for uterine arteries were significantly higher in URPL patients (P<0.001). The predictive accuracy of the indices mentioned above were 0.660, 0.802, 0.852, 0.837, 0.784, 0.929, and 0.929, respectively. Following LDA supplementation, URPL patients showed a significant reduction in resistance to endometrial and uterine artery blood flow (P<0.001).

Conclusion: URPL patients had impaired uterine perfusion. Doppler parameters are valuable in predicting women at high risk of URPL. LDA could be effective in improving endometrial receptivity.