Embryo quality was ranked as one of the most important predictors in determining the success of implantation, while clinically some patients may experience repeated IVF failure due to persistent poor embryo quality.Mitochondria, as the energy factory, is confirmed being a hallmark of quality and developmental potential of human oocytes, and decreased mitochondria copy number was reported to be associated with oocyte aging and dysfunctional mitochondria would be expected to influence the late stages of oocyte maturation and early embryogenesis.The objective of this study is to evaluate the effect of mitochondria transfer from bone marrow mesenchymal stem cell on the quality of oocyte.

This study is a pilot study to investigate the effect of autologous mitochondria transplantation for improving oocyte quality.

Design: randomized controlled trial. Setting: Assisted reproductive technologies unit. Patients: patients who is in accordance with the inclusion criteria, and not meet the exclusion criteria, who had repeated IVF treatment from Sep 2018 to Sep 2021.

Intervention: The comparison was made between mitochondria transfer（MIT) group and the control group, both groups are conducted with the GnRH-a super-long protocol for IVF treatment. MIT group injects autologous mitochondria from bone mesenchymal stem cells into oocyte.

Main outcome measures: The primary outcome of the study is live birth rate. The secondary outcomes were clinical pregnancy rate, number of oocytes retrieved, fertility rate, normal fertilization rate, rate of transferable embryo and good quality embryo rate.

Inclusion Criteria:

1. Women age >20 years and <43 years.
2. Anti-müllerian hormone（AMH） level ≥1.1 ng/ml.
3. Previous failed transfer cycle ≥2.
4. BMI>18kg/m2 and <25kg/m2.
5. Written informed consent.

Exclusion Criteria:

1. Abnormal uterine development, endometrial adhesion or previous endometrial dysplasia (<7mm)
2. Other medical diseases that cannot be pregnant.
3. Complicated with adenomyosis, endometriosis confirmed by surgery, ovarian endometriosis cyst ≥2 cm by ultrasound, all kind of malignant tumors or precancerous disease.
4. Untreated hydrosalpinx.
5. The man has definite factors that affect the quality of the embryo, such as persistent abnormal DNA fragment rate (>30%) and non-obstructive spermatozoa.
6. Intracytoplasmic sperm injection with donor.

Eliminate or falls off Criteria:

1.The number of retrieved oocytes <6.