Notes:①indicates P < 0.05 for the fresh embryo transfer group compared with the NC-FET group; ② indicates P < 0.05 for the fresh embryo transfer group compared with the HRT-FET group; ③ indicates P < 0.05 for the NC-FET group compared with the HRT-FET group; * indicates the fresh embryo group compared with the frozen-thawed embryo transfer group
Table 4 Comparison of placental pathological characteristics of three groups