In assisted reproductive technology, adenomyosis patients are characterized by lower clinical pregnancy rate, lower implantation rate and higher abortion rate. The purpose of this study is to explore whether low molecular weight heparin can reduce the abortion rate of adenomyosis patients in frozen thawed embryo transfer cycles.

Inclusion Criteria:

1. The basal serum level of FSH was less than 10 IU / L
2. Diagnosed with adenomyosis by ultrasound
3. The first frozen thawed embryo transfer cycle, by hormone replacement protocol
4. Transfer at least one high quality frozen embryo;
5. Patients agreed to use low molecular weight heparin after FET, and they were able to sign informed consent in person.

Exclusion Criteria:

1. With abnormal karyotype;
2. Accompanied with other uterine diseases: intrauterine adhesion, intramural myoma, moderate to severe endometriosis, congenital uterine malformation, endometrial tuberculosis, thin endometrium < 8mm on the day of transformation, etc;
3. PCOS, RIF patients;
4. There are indications of conventional anticoagulation or antiplatelet therapy, such as antiphospholipid syndrome, autoimmune diseases, coagulation dysfunction, etc;
5. There were contraindications to hormone replacement therapy and low molecular weight heparin;
6. Participating in other clinical studies;
7. Unable to follow-up