Atosiban in Women With Previous Implantation Failure and Abnormal Uterine Contractions

Participants/eligibility criteria Infertile women who fulfill all of the following inclusion criteria, based on the results and findings of the Atosiban 1 study are eligible for participation: 1. Scheduled for single blastocyst-stage embryo transfer, either in a fresh or frozen transfer cycle; 2. Have a history of one or more episodes of implantation failures in previous embryo transfer cycles; 3. Age between 20 and 40 years (inclusive); 4. Exhibit abnormal uterine peristalsis on transvaginal ultrasound performed on the morning of the scheduled blastocyst transfer, defined as either: high-frequency peristalsis (\>4 contractions per minute), or a negative wave pattern (fundus-to-cervix direction) at any frequency. 5. Each woman could only participate in one transfer cycle. Exclusion criteria 1. Immunologic or endocrine disorders including thyroid dysfunction, antiphospholipid syndrome, hyperprolactinemia and other severe systematic diseases (e.g., hypertension, diabetes, etc.) 2. Uterine malformations (e.g., intrauterine adhesions; unicornuate, bicornuate or septate uterus)； 3. Untreated hydrosalpinx or endometrial polyp； 4. Cycles that included in-vitro maturation or oocyte donation； 5. Prior participation in Atosiban 1 study； 6. Current participation in any other clinical trial； 7. Inability to provide informed consent to the study.