In order to further explore the clinical utility of endometrial receptivity array in patients with repeated implantation failure, the patients divide into the experimental group or the control group. In the experimental group, those patients undergo endometrial receptivity array. In the control group, those patients do not receive any treatment before next cycle of transfer. In the experimental group, according to the results of endometrial receptivity array, the transplantation time will be adjusted and retransplantation will be carried out. Statistical analysis of the two groups of primary endpoint and secondary endpoint are done.

In the field of assisted reproduction techonology, there are still 10% of patients with repeated implantation failure. In order to further explore the clinical utility of endometrial receptivity array in patients with repeated implantation failure, the patients divide into the experimental group or the control group. In the experimental group, those patients undergo endometrial receptivity array. In the control group, those patients do not receive any treatment before next cycle of transfer. In the experimental group, according to the results of endometrial receptivity array, the transplantation time will be adjusted and retransplantation will be carried out. In the control group, no intervention will be performed. Statistical analysis of the two groups of primary endpoint (clinical pregnancy rate) and secondary endpoint (endometrial implantation window evaluation results, embryo implantation rate, biochemical pregnancy rate, early abortion rate, ectopic pregnancy rate) are done. Through the comparative analysis of clinical outcomes to verify the clinical efficacy of endometrial receptivity analysis in patients with repeated implant failure, this method will provide a new treatment for repeated implant failure population.

Inclusion Criteria:

1. People with unexplained repeated implantation failure (3 or more times of transplantation, at least 4 or more high-quality embryos failed to conceive).
2. Age: 20-40 years old.
3. BMI: 19 - 24.
4. The thickness of endometrium is more than or equal to 7 mm.

Exclusion Criteria:

1. Known causes of embryo implantation failure, such as infection, reproductive tract malformation, uterine cavity factors, immune factors, hydrosalpinx, etc.
2. Decreased ovarian function (meet the following at least two criteria: ① 10u / L < basal follicle stimulating hormone (FSH) < 25U / L, and / or estradiol (E2) > 292.8pmol/l, and / or FSH / LH > 3; ② the number of antral follicles < 5-7 on the second to third day of menstruation; and (or) antimullerian hormone (AMH) < 0.5-1.1ng/ml.
3. People with genetic history.
4. Those who have done abortion and the histogenetic analysis are positive.