This is a single-center, prospective, randomized controlled study. Patients with single blastocyst transfer in the freeze-thaw cycle, aged from 20 to 38 years, with less than three transfers, and with HRT-cycle single D6 blastocyst transfer in the current cycle were enrolled as the study participants. They were randomized into two groups using an Excel table, and the efficacy was evaluated in a blinded manner by a third party who was unaware of the grouping; the data summary phase was performed by blinded statistical analysis with triple separation of the investigator, operator, and statistician.

Inclusion Criteria:

1. Aged 20 to 38 years.
2. Less than three transfers.
3. Undergoing HRT freeze-thaw cycle single blastocyst transfer in the current cycle.
4. Having consented to participate in this study and signed the informed consent form.

Exclusion Criteria:

1. Chromosomal abnormality in either the patient or their partner
2. Contraindications to hormone replacement therapy.
3. Patients with intramural myoma affecting the morphology of the uterine cavity, severe adenomyosis, endometriosis, congenital uterine anomalies, endometrial tuberculosis, intrauterine adhesion and other diseases significantly affecting embryonic implantation.
4. Currently participating in another clinical study.