Inclusion Criteria:

• abnormal uterine NK cell function;
• have one of the following medical history: unexplained recurrent spontaneous abortions (≥2 spontaneous abortions, including biochemical pregnancy), repeated implantation failure (failure of implantation of good-quality embryos in at least two IVF cycles), unexplained infertility, early-onset severe gestational hypertension or early-onset fetal growth restriction;
• have clear fertility desires;
• normal ovarian function or with frozen embryos;
• edometrium thickness measured by vaginal ultrasound before ovulation or at mid-luteal phase >= 7mm;
• 18kg/m^2 < Body mass index < 30kg/m^2;

Exclusion Criteria:

• using progesterone receptor modulator;
• chromosomal karyotype abnormalities in one spouse;
• severe endometriosis, uterine fibroids affecting the shape of the uterine cavity or the size of the whole uterus more than 2 and a half months of pregnancy, uterine malformation, uterine adhesion or thin endometrium;
• uncontrolled autoimmune diseases;
• abnormal blood coagulation function, abnormal liver and kidney function, or other uncontrolled basic diseases (hypertension, diabetes, thyroid disease, etc.) that the researcher access which may affect the progress of the study;
• history of pelvic malignant tumors;
• currently participating in other clinical studies;
• allergic to blood products.