[The impact of the number of previous miscarriages on embryo euploid rate and pregnancy outcomes in patients with unexplained recurrent pregnancy loss].

To investigate the impact of the number of previous miscarriages on embryo euploid rate and pregnancy outcomes after preimplantation genetic testing for aneuploidies (PGT-A) in patients with unexplained recurrent pregnancy loss (uRPL). A retrospective cohort study was conducted. 799 women with uRPL who underwent PGT-A for the first time between January 2015 and December 2021 at the Reproductive center of Shandong University were enrolled. These patients were divided into three groups according to the number of previous miscarriages (2, 3, and≥4). Stratified analysis was conducted according to female age (≤37 years and>37 years). The embryo euploidy rate, good-quality blastocyst formation rate, cumulative live birth rate, and cumulative clinical pregnancy loss rate of three groups were compared in younger and older patients, respectively. Meanwhile, the cumulative live birth rate, clinical pregnancy loss rate, and embryo euploidy rate were analyzed by multivariate logistic regression analysis. Patients' age was (34.7±5.1) years old. In the three groups with 2, 3 and ≥4 previous miscarriages, there was no significant difference in the embryo euploidy rate between groups in the younger [48.9% (539/1 103), 50.6% (354/700) and 52.1% (152/292), =0.567] and older [26.2% (103/393), 28.8% (55/191) and 20.5% (16/78), =0.377] age population. Compared with 2 and 3 previous miscarriages, the cumulative live birth rate was significantly decreased [52.6% (153/291), 52.8% (93/176) and 34.3% (25/73), =0.014] and the cumulative clinical pregnancy loss rate was significantly increased [15.8% (31/196), 15.3% (18/118) and 46.9% (23/49), <0.001] in younger women with ≥4 miscarriages. After adjusting for maternal age, BMI, AMH, endometrial thickness on hCG trigger day and antral follicle count, the number of previous miscarriages ≥4 was a relevant factor for cumulative live birth rate (=0.461, 95%: 0.263-0.807, =0.007) and the cumulative clinical pregnancy loss rate (=4.382, 95%: 2.165-8.873, <0.001) in younger patients, but it was not significantly correlated with the cumulative live birth rate, cumulative clinical pregnancy loss rate and embryo euploidy rate in patients with advanced age. In uRPL patients,≥4 previous miscarriages decreased cumulative live birth rate and increased cumulative clinical pregnancy loss rate in women aged≤37 years old.