Cryopreservation (Embryo Freezing)

What is Cryopreservation (Embryo Freezing)?
Cryopreservation, commonly known as embryo freezing, is a process used in Assisted Reproductive Technology (ART) to preserve embryos by cooling them to sub-zero temperatures for future use. In surrogacy, this technique allows embryos created through in vitro fertilization (IVF) to be stored and later transferred to a gestational surrogate’s uterus, offering flexibility in timing and improving pregnancy outcomes.

How Does Cryopreservation Work?
During an IVF cycle, eggs are retrieved, fertilized with sperm, and cultured into embryos — often to the blastocyst stage (day five or six). High-quality embryos not immediately transferred are frozen using a rapid-freeze method called vitrification. This involves immersing embryos in cryoprotectants to prevent ice crystal formation, then storing them in liquid nitrogen at around -196°C. When ready, the embryos are thawed for a Frozen Embryo Transfer (FET) into the surrogate’s or intended mother’s uterus, coordinated with her menstrual cycle and hormonal preparation.

What’s Its Role in Surrogacy?
Cryopreservation is a cornerstone of gestational surrogacy, enabling intended parents to create embryos in advance and transfer them to a surrogate at an optimal time. It supports scenarios like delayed transfers due to medical, legal, or logistical reasons, and allows multiple attempts from a single IVF cycle without repeated egg retrievals. It also facilitates Preimplantation Genetic Testing (PGT), as embryos can be biopsied, frozen, and transferred after results are confirmed, ensuring healthier pregnancies for surrogates.

What Are Common Features?

• Vitrification: A fast-freezing technique that preserves embryo viability better than older slow-freezing methods.
• Storage Duration: Embryos can remain viable for years, with successful pregnancies reported after over a decade in storage.
• Frozen Embryo Transfer (FET): Thawed embryos are transferred in a separate cycle, often with higher success rates than fresh transfers.
• Embryo Selection: Freezing allows time for genetic screening or choosing the best embryos for transfer.
• Backup Plan: Provides options if initial transfers fail or for future siblings.

Where Did It Come From?
Cryopreservation began shaping reproductive medicine in the 1980s, building on earlier sperm-freezing successes. The first human embryo freeze leading to a live birth occurred in 1984 at Monash University in Melbourne, Australia, under Alan Trounson’s team. Vitrification, a game-changer, was refined in the 1990s in Osaka, Japan, by researchers like Masashige Kuwayama, improving embryo survival rates. By the 2000s, clinics in the United States — notably in San Francisco, California — and Cambridge, England, adopted vitrification widely, making cryopreservation a standard in surrogacy and IVF globally.

Who Uses Cryopreservation?

• Gestational Surrogates: Carry thawed embryos, benefiting from simplified transfer timing.
• Intended Parents: Preserve embryos for surrogacy, future pregnancies, or fertility preservation (e.g., before medical treatments).
• Fertility Clinics: Store embryos to optimize IVF success and support genetic testing.

What Are Benefits and Considerations?

• Benefits: Increases flexibility, reduces the need for repeated IVF cycles, and supports single-embryo transfers to lower multiple pregnancy risks.
• Challenges: Not all embryos survive thawing (though vitrification yields 95%+ survival rates), and storage fees can accumulate.
• Emotional Impact: Offers hope for future pregnancies but may raise decisions about unused embryos, causing stress for intended parents.

What About Legal and Financial Aspects?
Cryopreservation costs $1,000-$2,000 initially in the U.S., with annual storage fees of $500-$1,000. FET cycles range from $3,000-$7,000, excluding surrogacy fees. Legal agreements — costing $5,000-$10,000 — specify embryo ownership, storage duration, and disposition (e.g., donation, destruction) in surrogacy contracts. Laws vary: California and Colorado streamline embryo transfers, while countries like Germany restrict cryopreservation, impacting international surrogacy.

Why Does It Matter?
Cryopreservation empowers surrogates and intended parents with timing control and cost efficiency, making surrogacy more accessible and effective. For potential surrogates, understanding embryo freezing clarifies the process, boosting confidence in their role. By showcasing this technology’s precision, agencies build trust and authority, guiding clients toward informed family-building choices.

Related Terms

• Frozen Embryo Transfer (FET)
• In Vitro Fertilization (IVF)
• Gestational Surrogacy
• Preimplantation Genetic Testing (PGT)
• Blastocyst

Cryopreservation freezes moments of hope, preserving embryos to create families when the time is right for surrogates and intended parents alike.