What are the Differences between Freezing Eggs vs. Embryos?

embryos fetus

As more people are considering preserving their fertility for the future, many are wondering about the differences between freezing eggs and embryos, and which option is best for them. It is estimated that around one-third of all fertility treatments and procedures that took place in the US in 2019 were for patients who wanted to freeze their eggs or embryos for future family planning. These procedures give women and people who have periods more choice around when they have children and how they will conceive, but they are also quite different and there is a lot to consider, especially with the costs involved. Dr. Barbara Levy, Flo board member and clinical professor of obstetrics and gynecology, explains the differences between freezing eggs and embryos and some of the questions you should ask your healthcare provider before starting treatment.

What’s the difference?

The process of choosing between freezing eggs or embryos can be confusing, but there is a significant difference between the two. When you freeze your eggs, they are unfertilized. An egg is only half of what is needed to make a baby, while an embryo is an egg that has been fertilized and has the potential to develop into a baby. When deciding between the two, you should consider your personal circumstances and the latest research. If you don't know who you want to have children with, freezing your eggs may give you the freedom to start thinking about having a baby when you've met someone or are ready to pick a sperm donor. On the other hand, if you know you'd like to have children with a current partner but aren't in a position to do so right away, freezing embryos could be a better option. Research has compared freezing eggs vs. embryos based on which treatment option is more likely to lead to babies being born. Factors such as age and recent developments in fertility treatment and freezing technology should also be considered.

How to prepare

Before freezing your eggs or embryos, it's necessary to stimulate the follicles in your ovaries to produce as many eggs as possible. Follicles are small sacs filled with fluid in the ovaries, and each ovary has around 8 to 15, and generally, each follicle has the ability to release an egg during ovulation. To begin this process, you will be given instructions by your clinic and will inject follicle-stimulating hormones for 8 to 14 days. A sonographer will then regularly check the size of your follicles, and your healthcare provider will monitor your estrogen levels through blood tests and an internal ultrasound. The number of eggs produced may vary from person to person, so try not to compare yourself to others. Once at least three of your follicles are big enough, your healthcare provider will advise you to inject yourself with a trigger shot of a hormone known as human chorionic gonadotropin, which triggers ovulation and egg maturity. The eggs will be collected approximately 36 hours later in a procedure called egg retrieval. If you feel nervous about egg stimulation, speak to your clinic, they will be able to provide tips and advice to make the process easier.

How are eggs collected and fertilized?

Egg retrieval, also known as egg collection, is the next step after egg stimulation. This is a small procedure that takes around 20 minutes and is done while the patient is under sedation. Your healthcare professional will use an internal vaginal ultrasound to examine the follicles and use a suction device with a thin needle to remove the eggs from the follicles. Not every follicle will contain an egg, but as many as possible will be collected. After the procedure, your doctor will inform you of how many eggs were collected. It is common to experience some bleeding or cramping after the procedure, but if you're concerned, speak to your medical team. If you choose to freeze your eggs, the clinic will assess which eggs are mature and freeze them promptly. If you choose to freeze embryos, the eggs will be fertilized with sperm and will grow for 5 to 7 days under the watch of an embryologist. Some clinics may choose to freeze embryos slightly earlier and then grade the embryos for quality before freezing. Not every embryo will make it to this stage, which is normal. After the egg collection, your period should arrive within two weeks and your cycle should return to normal the following month.

How are eggs and embryos frozen?

Embryos and eggs are both frozen through a process called vitrification, which is a flash-freezing method. This method stops all biological processes and is why freezing eggs is referred to as "freezing time." The cells are cooled to very low temperatures, -196 C or -320 F, and placed in individual straws. They are then plunged into liquid nitrogen for storage, which is done with the use of cryoprotective agents to protect the cells from ice crystals. Vitrification is a newer method of freezing eggs and embryos, before it was developed, a slower freezing method was used. It is important to discuss the storage process with your healthcare provider before undergoing the freezing process.

Freezing embryos

The process of freezing embryos varies depending on the clinic and the stage of development at the time of freezing. Typically, embryos are frozen at either 3 days after fertilization when they are six to eight cells or 5 to 7 days after fertilization when they have reached the blastocyst stage, which is between 50 and 200 cells. According to Dr. Levy, research has shown that embryos frozen at day 5 have a higher success rate when transferred to the uterus compared to those frozen at day 3. However, it is important to consult with your healthcare provider to understand the specific approach and reasoning used by the clinic you have chosen.

Which is better: freezing eggs vs embryos?

It is important to consider what your ideal outcome is when thinking about preserving fertility. If you're single or unsure of who you want to have children with, freezing eggs may be the best option. On the other hand, if you plan to have children with a current partner in the future, freezing embryos may be a better choice. Consulting with a fertility specialist and talking to friends and family can help you make a decision. Additionally, it is important to consider how your fertility clinic will handle thawing and treating your eggs or embryos. Research has shown that eggs can be damaged during the thawing process, and it is crucial to ensure your clinic has experience in thawing and not just freezing eggs or embryos.

The cost

The cost of fertility treatment, including egg and embryo freezing, can vary greatly depending on location. In the US, the cost of the drugs alone can range from $4,000 to $5,000 for one cycle, with egg collection and freezing costing upwards of $10,000. Storage costs can also be around $800 per year. In the UK, IVF is available through the NHS if certain criteria are met, but fertility preservation is not, and costs for egg or embryo freezing can range from £3,350 for the collection and freezing process to £125 to £350 per year for storage. In Canada, costs can range from CA$5,000 to CA$15,000 and in Australia around AU$5,000 to AU$7,000. It is important to speak with a healthcare provider to understand the costs and any potential financial support available.

The takeaway

It's normal to feel overwhelmed when considering the costs and procedures involved with freezing eggs and embryos. Dr. Levy advises not to fixate on global statistics and instead focus on your own results with your specific clinic, embryologist, and lab. Your healthcare provider should be able to answer any questions you have and provide information on recommended egg or embryo freezing numbers, treatment cycles, costs, financial support options, health risks, side effects, age limits, and storage length.