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    A Guide to Egg and Embryo Cryopreservation in Oncofertility Care

    Expert Perspectives · Keira Smith · 2026-04-20

    For patients undergoing cancer treatment, egg and embryo cryopreservation are the gold standards of fertility preservation. While the biological starting point is the same, the path a patient chooses depends on their individual situation, long-term goals, and even genetic considerations. Recently Dr. Meaghan Delaney, Co-Director of the Oncofertility Program at Boston IVF, sat down with Oncology Data Advisor to share an overview of the role of fertility preservation in cancer treatment. In this interview, she joins us again to delve into the processes of egg and embryo cryopreservation and how clinicians can help their patients navigate the decisions. 

    The Decision Tree 

    The first branch of the decision tree is developmental: prepubertal patients are directed toward tissue cryopreservation, while post-pubertal patients choose between eggs and embryos. For patients not planning to start a family in the immediate future, oocyte cryopreservation is the standard. For patients ready to start sooner, the choice can be more complex. Dr. Delaney notes that while creating embryos with a partner is common, relationship changes can later complicate a patient’s access to those embryos. Consequently, some patients choose to freeze a mix of both eggs and embryos to preserve maximum autonomy. “These conversations are sometimes hard to have with a patient and/or their partner, but it’s important to have for sure,” Dr. Delaney said.

    The Clinical Protocol

    A primary concern for oncologists is the potential delay in cancer treatment while undergoing fertility preservation. Dr. Delaney emphasizes that the entire stimulation and retrieval process typically fits within a 14-day window.

    The process involves:

    • Ovarian Stimulation: Patients self-administer follicle-stimulating hormone (FSH) injections for approximately 10 days to stimulate multiple follicles.

    • Monitoring: Patients visit the clinic 3-4 times for transvaginal ultrasounds and same-day blood work to adjust dosages.

    • The Trigger and Retrieval: Once follicles reach the target size, a "trigger shot" matures the eggs. Retrieval is performed under conscious sedation via ultrasound-guided needle aspiration. "Patients have no incisions. They wake up and go home the same day," said Dr. Delaney.

    • Fertilization (Optional): If creating embryos, eggs are fertilized via conventional in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) and grown to the blastocyst stage (5-7 days) before freezing. 

    Managing Hormone-Sensitive Cancers and Side Effects 

    Another concern for clinicians is the high estrogen levels associated with ovarian stimulation, particularly in breast or gynecologic cancers. Dr. Delaney reassures that "we can use medications to keep those levels low so that there's no growth of their tumors." Additionally, medications are used to mitigate bloating and prevent ovarian hyperstimulation syndrome (OHSS), ensuring the patient can transition quickly to their oncology treatments.

    Predicting Success

    Success in oncofertility is dictated by two primary variables: the patient’s age at the time of freezing and the total number of units stored. Because egg quality declines naturally—and more sharply after age 35—younger patients generally require fewer eggs to achieve a high probability of a future live birth. 

    "At 30 years old, one out of three or four eggs is going to make a pregnancy," Dr. Delaney explains. By age 40, that ratio shifts to one in eight or ten. For embryos, pre-implantation genetic testing for aneuploidy (PGT-A) can provide more certainty: "If you have a normal embryo, it has a 65% implantation rate." For patients with known hereditary cancer syndromes, pre-implantation genetic testing for monogenic disorders (PGT-M) can also be used to screen embryos for specific oncogenes before cryopreservation.

    Conclusion

    “The general takeaway I want to share is that these processes don’t take a long time; they take two weeks or less,” Dr. Delaney shared, underscoring that fertility preservation can be feasibly done without causing delays to cancer treatment.

    Key Takeaways

    • The Two-Week Rule: Most fertility preservation cycles can be completed in 14 days or less, rarely requiring a significant delay in chemotherapy.

    • Autonomy Matters: Encourage single or young patients to consider egg freezing to maintain full control over their future reproductive material.

    • Hormone Safety: Protocols can be modified with letrozole or other agents to protect patients with hormone-sensitive malignancies.

    • Genetic Insights: Embryo freezing allows for PGT-M testing, which is vital for patients carrying BRCA or other pathogenic variants.

    • Quantity vs Quality: Older patients or those with low ovarian reserve may benefit from a second cycle if the oncology timeline permits.

    About Dr. Delaney

    Meaghan Delaney, MD, MA, is the Co-Director of the Oncofertility Program at Boston IVF, a part of IVI RMA North America. She is double board-certified in Obstetrics/Gynecology and Reproductive Endocrinology/Infertility. Dr. Delaney specializes in all aspects of fertility care, and her research interests include analyzing disparities in fertility knowledge and care among different demographics.