Embryo freezing as fertility preservation
Most fertility clinics freeze embryos as part of their services. However, not every clinic freezes the embryos themselves; some send them to a separate fertility lab for freezing. This article covers the most commonly asked questions about embryo freezing, including where it happens, why patients freeze embryos, and how the process works.
Where Are Embryos Frozen?
Specialists called embryologists freeze embryos in a lab. Depending on your fertility clinic, they may freeze your embryos in-house or partner with a separate lab service. While third-party lab services can be excellent, every instance of transporting an embryo creates the opportunity for human error. For this reason, we built a state-of-the-art embryology lab inside our PNWF Seattle fertility clinic. This means we perform all our embryology lab services, including fertilization and freezing, in the same building as our egg retrievals and embryo transfers. By doing this, we reduce the chances for human error and maintain our strict quality control standards at every step of the way.
Why Do People Freeze Embryos?
Embryo freezing is one form of fertility preservation, along with egg and sperm freezing. People freeze their embryos for a number of reasons, including:
- Age
- Military deployment
- Illness treatments such as chemotherapy
- Gender affirmation treatments (surgery or hormonal)
In these cases, patients freeze embryos to hopefully have the option to pursue a pregnancy in the future when circumstances might make it difficult or impossible to become pregnant naturally. Some patients also freeze additional embryos left over after going through IVF treatments. You can store these embryos, use them in future IVF cycles, or donate them.
When Do Fertility Clinics Freeze Embryos?
In most cases, we freeze at the blastocyst stage of development. This happens around 5-7 days after fertilization, when the rapidly dividing cluster of cells forms into an early stage of the embryo. Freezing the embryo at this point increases its chance of surviving the freezing and thawing process. Waiting until the blastocyst stage also allows for pre-implantation genetic testing (PGT-A), if chosen. In PGT-A, embryologists take a few cells from each blastocyst for testing. The lab then freezes the blastocysts while the test results process, which can take a couple weeks.
How Do Fertility Clinics Freeze Embryos?
The majority of fertility clinics freeze embryos through a process called vitrification. This involves using liquid nitrogen to freeze the embryos almost instantly. Clinics used to use a process called slow-freezing, which involved gradually cooling the embryo over the course of a couple hours. However, slow-freezing can create ice crystals which can damage the embryo during thawing. Freezing the tissue very quickly helps avoid ice crystal formation. For this reason, vitrification is much more successful, and now used much more commonly.
How Long Can Fertility Clinics Store Embryos After Freezing?
In theory, frozen embryos can survive in storage indefinitely. The freezing process preserves embryos in time, keeping them from aging. Currently, the longest-frozen embryos that have resulted in a live birth were frozen for 30 years. Of the five embryos frozen in 1992, three survived the thawing process, and two successfully implanted, resulting in twins born in October 2022.
Can Frozen Embryos Turn into Successful Pregnancies?
Thanks to technological advances, frozen embryo transfers at PNWF have roughly the same success rate as fresh embryo transfers. The embryo’s quality and viability should stay the same while it is frozen. These factors, and with them the embryo’s chances of successful implantation, strongly depend on the age of the person who provided the egg at the time of fertilization. For instance, a frozen embryo developed from a 26-year-old person’s egg has a greater chance of success than one from a 38-year-old’s egg, no matter how long each embryo was frozen.
Our Fertility Clinic Offers Embryo Freezing With Unmatched Success Rates
PNWF offers the best in embryo fertilization, freezing, storage, and thawing techniques. Through our onsite lab, we provide a full range of embryology services to meet your fertility goals. For more information on embryo freezing, contact us today.
