retrieving eggs for freezing

Embryo Freezing: A Comprehensive Guide

Learn about the embryo freezing process, embryo vs. egg freezing for how long embryos can be frozen, and other considerations.

September 20, 2023


In the world of reproductive technology, advancements have made it possible for individuals and couples to preserve their fertility for future family planning. One of the remarkable innovations in this field is embryo freezing, also known as embryo cryopreservation. In this blog, we'll dive into the intriguing world of frozen embryos, exploring the process, advantages, and essential considerations.

What is an Embryo Freezing?

Embryo freezing is a fertility preservation method where embryos are created in the lab from eggs retrieved and fast-frozen at a very low temperature through a process known as vitrification. This technique allows for the storage of embryos for an extended period until they are ready to be used in assisted reproductive procedures like in vitro fertilization (IVF).

Embryo Freezing Process

The embryo freezing process involves several crucial steps:

  • Ovarian stimulation: during this stage, you are taking fertility medications (hormonal injections) to stimulate the growth of multiple follicles that can be further retrieved and fertilized. You should expect to go to the fertility clinic every few days for monitoring appointments (blood work and ultrasound).
  • Egg retrieval: When the follicles reach the appropriate size, you take a trigger shot approximately 35-36 hours before your retrieval to promote ovulation. The retrieval itself is a simple 20-30-minute procedure done under anesthesia when the fluid containing follicles is collected from the ovaries.
  • Embryo fertilization and culture: The follicles retrieved are inspected in the embryo lab to select mature eggs. Then, mature eggs are combined with the prepared sperm sample in a laboratory dish to create embryos through either standard IVF or intracytoplasmic sperm injection (ICSI). The resulting embryos are grown in a controlled environment for a few days to ensure they are healthy and developing properly.
  • Cryopreservation: Healthy embryos are then fast frozen using the vitrification technology and stored in liquid nitrogen at temperatures as low as -196°C (-321°F). 

How Long Can Embryos Be Frozen?

One of the most common questions about frozen embryos is how long they can be stored while remaining viable. The answer depends on various factors, including the quality of the embryos and the storage conditions. Generally, embryos can be frozen for an extended period, often several years, without a significant decrease in their viability. Based on existing research, the time you keep your embryos frozen doesn't affect the results of your future IVF.

Frozen Embryos vs. Frozen Eggs: Which is Better?

  • Embryo Freezing: This is a great option for couples who are planning to have kids together in the near future or later in life. The main benefit of embryo freezing is the amount of data that you have. While with egg freezing, it's hard to predict how many eggs will fertilize and end up as healthy embryos, with embryo freezing, you know exactly how many embryos you have that can also be tested for any genetic diseases or abnormalities.

Frozen embryos also have a little higher thawing survival rate of around 85%-95%, whereas frozen eggs have 80-90%.

  • Egg Freezing: This is a viable choice for those who wish to preserve their fertility but do not have a partner or are not ready yet to start a family with their current partner. It provides more flexibility but has less certainty than embryo freezing. While it is not a guarantee, current studies show promising results that with at least 20 eggs frozen before the age of 38, you can reach up to 70% probability of live birth. 

Ultimately, the choice between freezing eggs or embryos depends on individual circumstances and future family planning goals. If you are ready to 

How Many Embryos Should I Freeze?

The number of embryos you should freeze depends on your specific situation and family plans. You should discuss it with your fertility specialist, who would be able to give you more specific guidance based on your individual situation. Typically, having a surplus of high-quality embryos is reassuring, but the exact number will vary from person to person.

Success Rates of Embryo Freezing

The success rate of embryo freezing largely depends on the quality of the embryos and the expertise of the fertility clinic. Generally, the success rates for using frozen embryos in IVF procedures are promising, with many resulting in successful pregnancies and healthy births. Check how the success rates of different clinics compare to the national level.


Embryo freezing, or cryopreservation, has revolutionized the field of reproductive medicine. It provides individuals and couples with the opportunity to preserve their fertility and plan for future family-building endeavors. Whether you choose to freeze embryos or eggs, it's essential to consult with a fertility specialist to make informed decisions about your reproductive journey. Book a first consultation with a fertility doctor.

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