IVF, Egg Freezing

Fertility Preservation Options: Egg Freezing vs. Embryo Freezing

Berry

7 min read

When planning your fertility treatment, finding all of the statistics and information that you need all in one place sometimes feels impossible. You just want to make an educated decision about which treatment is right for you. So, to make your decision a little easier, we did the research for you! Of course, use this information in conjunction with recommendations from your doctor based on your age and medical history.

Egg Freezing vs. Embryo Freezing

When thinking about preserving your fertility, there are 2 options: freeze eggs or freeze embryos. For both processes, the first half is the same. You’ll spend about 10-14 days taking ovarian stimulation medications to grow many eggs to maturity within the ovaries. You’ll go into your doctor’s office for ultrasounds and bloodwork to track your body’s response to the medications. When your doctor determines that the eggs are likely to be mature based on your ultrasound and bloodwork, you’ll take a trigger shot in preparation for your egg retrieval. 

The real difference between egg freezing and embryo freezing comes after the egg retrieval. 

In egg freezing, once the eggs are retrieved, the embryologist sorts through and examines each of the eggs. Then the eggs that are in a cell division stage known as metaphase II or "MII" will be frozen and the others will be discarded. 

MII eggs have the best chance of being fertilized later on when you’re ready to use your eggs to create embryos. 

The eggs will remain frozen until you decide you want to thaw and fertilize them in an attempt to create embryos. Once the embryos are created, you can plan an embryo transfer cycle to try to get pregnant.

For embryo freezing, once the eggs are retrieved, the eggs are fertilized with sperm from either your partner or a sperm donor. This can be done through either combining the eggs with the sperm and allowing fertilization to occur naturally or through a process of manual fertilization done by the embryologist known as Intracytoplasmic Sperm Injection or ICSI. After fertilization, the embryos are allowed to culture in the lab for 5-7 days. During culture, the embryos have the opportunity to grow to the Blastocyst stage. This stage is optimal for biopsying for genetic testing as well as freezing the embryos for future embryo transfers.

Not all embryos make it to the blastocyst stage. Depending on your personal situation, the embryology lab may recommend freezing the embryos sooner (at an earlier stage of development) or embryos that stop growing may need to be discarded. It’s also important to know that some embryos that make it to blastocyst aren’t able to be frozen due to other defects within the embryo that are not compatible with pregnancy.

Both egg freezing and embryo freezing provide the opportunity to preserve your fertility. As discussed, the processes begin in a similar way, but there are some distinct differences. One of them is the cost.

Cost per Cycle

Thaw Rate

A key difference between freezing eggs and embryos is the rate at which each can survive the thaw process: embryos have a higher survival rate than eggs.

In fertility, thawing is the process done to use previously frozen eggs and embryos. When the lab thaws the eggs or embryos, the process starts by removing the tissue from the liquid nitrogen tanks. Then, thawing compounds are added into a dish with the tissue to start the process and help prevent damage to the cell structures. The dish is warmed to aid in the thawing. Once thawed, the cells are placed in a culture media to finish the process.

So “surviving the thaw” in the chart below means that the eggs or embryos were able to be frozen and thawed without the kind of damage to the cell(s) that would disqualify it from use in creating a pregnancy. 

Live Birth Rate

Another factor to consider is how likely you are, based on your age, to have an actual successful birth based on the number of frozen embryos or eggs you’ve obtained. This is commonly referred to as Live Birth Rate

Live Birth Rate for Egg Freezing

Calculating the live birth rate precisely is hard for two reasons. First, the data is scarce because elective egg freezing is still relatively new (The American Society for Reproductive Medicine (ASRM) stopped considering egg freezing “experimental” to “ in 2012) and many people who have frozen their eggs have not had to thaw and use them yet to get pregnant. Second, it depends on two factors: your age and the number of eggs extracted. The following chart gives you a rough sense of how  those two numbers factor into a calculation for live birth rate:

Now you might be wondering how many eggs are extracted per cycle. Again, the data on this is hard to generalize because outcomes can vary quite drastically, but this chart gives you a rough sense of the average:

Note that egg freezing is usually not recommended for those above 40, which is why there is very little data for those in this age category. In many cases, clinics have a policy regarding the maximum age for egg freezing.

We recommend reading this article on egg freezing, which has more charts based on age and other factors you can explore. Just keep in mind some of the data is based on models extrapolated from patients going through IVF. 

Live Birth Rate for Embryo Freezing

Similar to naturally conceived pregnancies, embryo transfer success rates vary based on age. The success of embryo transfers has a lot to do with the health and anatomy of the person carrying the pregnancy as well as characteristics of the embryo itself. The success of embryo transfers are typically quantified by the live birth rate (what percentage of embryo transfers result in the birth of a live infant).

Preimplantation Genetic Testing (PGT) is a way to take a few cells from an embryo and analyze the chromosomes within it. There are a few types of PGT, some that look for the correct number of chromosomes (PGT-A) and others that look for specific genetic disorders that could be passed down by the parents (PGT-M, PGT-SR). The chance of a successful pregnancy increases when a normal or Euploid embryo is transferred. As you age, the percentage of embryos that are euploid decreases.

Additional considerations

Other than statistics, there are a few additional things to think about when determining the next steps in your treatment journey. 

More Egg Freezing Research

Since 2012 when the American Society of Reproductive Medicine (ASRM) removed the label of “experimental” from egg freezing, the procedure has become more and more popular. According to the New York Times, 13,000 people froze their eggs in 2020, which is about 5 times as many cases as occurred in 2012. 

Even with so many cases occurring yearly, there still isn’t a large amount of research available that looks into the success of the use of the eggs that were frozen in elective egg freezing cycles. Many of the eggs have not yet been thawed to attempt fertilization and ultimately pregnancy, and some patients have created families through other means and have not needed to use their frozen eggs. So the success of these frozen eggs remains unknown.

As time goes on and more and more people begin to use their frozen eggs to try to get pregnant, more studies can be conducted to provide even better recommendations for the number of eggs to freeze and the likelihood of a pregnancy resulting from those eggs based on age. 

Until then, we know that freezing eggs or embryos isn’t a guarantee, but they are a great insurance policy that gives you the opportunity to preserve your fertility and the chance to create a family on your own timeline.

Sources

Assisted Reproductive Technology (ART) DataAssisted Reproductive Health Data: Clinic | DRH | CDC.” n.d. Nccd.cdc.gov.

Blum, Dani, and Nicole Stock. 2022. “What to Know before You Freeze Your Eggs.The New York Times, December 23, 2022, sec. Well. 

Cascante, Sarah Druckenmiller, Jennifer K. Blakemore, Shannon DeVore, Brooke Hodes-Wertz, M. Elizabeth Fino, Alan S. Berkeley, Carlos M. Parra, Caroline McCaffrey, and James A. Grifo. 2022. “Fifteen Years of Autologous Oocyte Thaw Outcomes from a Large University-Based Fertility Center.Fertility and Sterility 118 (1): 158–66.

Getting Real about IVF Success Rates.” n.d. Ro. Accessed February 3, 2023. 

Gupta, Alisha Haridasani, and Dani Blum. 2022. “Hope, Regret, Uncertainty: 7 Women on Freezing Their Eggs.The New York Times, December 23, 2022, sec. Well. 

How Much Does IVF Cost?” 2021. Forbes Health. September 28, 2021..