Inclusion Criteria:
1. Able to communicate well with investigators, understand and comply with trial requirements, participate voluntarily, and provide signed informed consent after full understanding.
2. Married women aged 36 to 40 years (exclusive of boundary values).
3. Normal ovarian function: AMH ≥ 1.1 μg/L and basal FSH \< 10 IU/L.
4. Scheduled to undergo controlled ovarian stimulation (COS) and IVF/ICSI using a fixed antagonist protocol combined with Corifollitropin alpha N02 injection.
Exclusion Criteria:
1. ≥3 previous cycles of controlled ovarian stimulation (COS)
2. Recurrent pregnancy loss: ≥3 previous pregnancy losses (including spontaneous abortion, biochemical pregnancy, and missed abortion).
3. Repeated implantation failure: ≥3 embryo transfer cycles (fresh or frozen) or failure to achieve clinical pregnancy after transfer of ≥4 high-quality embryos in total.
4. High risk of ovarian hyperstimulation syndrome (OHSS), defined by any of the following:
* Diagnosed with polycystic ovary syndrome (PCOS);
* Total number of AFC in both ovaries \>20 on Day 2-3 of menstruation; ③ Previous cycle cancellation (including canceled embryo transfer) due to high ovarian response or high OHSS risk; ④ History of OHSS; ⑤ Other conditions judged by the investigator to confer high OHSS risk after comprehensive evaluation.
5. Poor ovarian function, defined by any of the following:
① Previous poor ovarian response (≤3 oocytes retrieved following conventional full-dose gonadotropin stimulation);
② Total AFC in both ovaries \<5.
6. Presence of any reproductive, endocrine, or immune disorders that may affect pregnancy, as assessed by the investigator.
7. Abnormal uterine bleeding.
8. Presence of systemic diseases (e.g., cardiovascular, digestive, neurological, hematological disorders) deemed unsuitable for study participation by the investigator, or severe diseases incompatible with pregnancy.
9. Hypersensitivity or history of allergy to active ingredients or excipients of gonadotropins (Gn), GnRH antagonists, or progesterone preparations, or with documented contraindications to these medications.
10. History of alcoholism, heavy smoking, drug addiction, or substance abuse.
11. Scheduled to undergo preimplantation genetic testing (PGT).
12. Currently participating in another clinical trials and receiving investigational products.
13. Any other conditions deemed by the investigator to render the subject unsuitable for trial participation based on safety considerations.
