Embryo freezing is commonly performed as part of infertility treatment following IVF or ICSI procedures.
In the past, embryos were frozen primarily when a high number of eggs were retrieved, resulting in multiple embryos, or in cases where the uterus was not suitable for transfer at the time such as during the risk of ovarian hyperstimulation syndrome (OHSS). However, recent studies have shown that pregnancy rates are often higher with frozen embryos compared to fresh transfers. As a result, today, the majority of embryos created during IVF or ICSI cycles are frozen and transferred in subsequent cycles.
Embryo freezing is also considered one of the most effective methods for fertility preservation. It is strongly recommended for couples who wish to delay childbearing due to economic, career, educational, or personal reasons or for medical reasons such as cancer.
How the Embryo Freezing Process Works
Fertilized eggs are frozen for future use on either day 3 or day 5 after fertilization.
Step-by-step process:
- Embryos created through IVF or ICSI are cultured in special lab incubators for 3 to 5 days.
- A cryoprotective solution (similar to antifreeze) is added to prevent the formation of ice crystals within the cells.
- Embryos are then loaded into thin, sterile straws.
- Each straw is labeled with the couple’s identification.
- The straws are then placed into tanks filled with liquid nitrogen at –196°C (–321°F), where they are rapidly frozen.
A fascinating fact: Frozen embryos remain biologically the same age as when they were frozen. They do not age over time.