The differences between egg freezing and embryo freezing

jennifer aniston
Egg freezing vs. embryo freezing, explainedAxelle/Bauer-Griffin - Getty Images

According to recent reports, the pandemic prompted a sharp rise in women freezing their eggs for fertility prevention. At some UK clinics, enquiries have increased by 50 per cent, and with Jennifer Aniston recently speaking out about her experience with IVF – and wishing she had frozen her eggs – that's a stat which might further advance.

Another option for those wanting to preserve their fertility is embryo freezing, a treatment that has been around for much longer than egg freezing, and is touted by some experts as more reliable, though it has different consent and autonomy implications.

Here we explain the key differences between embryo and egg freezing, while three specialists – embryologist Sandy Christiansen, fertility expert Jenny Saft, and co-founder of the Fertility Academy Dr Amin Gorgy – share their insights on the treatments, and advise on how to decide which might be right for you.

What is egg freezing?

Egg freezing is a procedure that involves collecting a woman’s eggs from her ovaries and freezing them for use in the future.

There are a number of reasons why women may choose to freeze their eggs. Often, women want to preserve their fertility so that they can try and have a family when they are ready at a later date. This is known as ‘social’ egg freezing. Women may also choose to freeze their eggs before undergoing medical treatment that may impact their fertility, such as chemotherapy. When a woman is ready to use the frozen eggs, they are defrosted and fertilised, before being transferred to the womb.

According to Dr Amin Gorgy, the average age of women coming to him for social egg freezing is 37 – but, he says, that's changing.

"Recently younger women are coming to me to freeze their eggs, particularly those who don't feel quite settled career-wise," he explains. "More women have become aware of the availability of the services and the good success rate of using frozen eggs."

What is embryo freezing?

Embryo freezing is a procedure that allows women to store fertilised eggs for later use. These eggs will have been fertilised in a laboratory with either a partner or donor’s sperm. Most often, when people undergo in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI), good quality embryos are left over after embryo transfer. These embryos can be frozen for use in the future, should the treatment not work or should people wish to try for another baby.

Other people may choose to freeze their embryos to preserve fertility, so they can use them to try to get pregnant at a later date. This is known as the ‘freeze all’ or elective frozen embryo transfer (FET) technique. In certain cases, patients with specific health conditions may benefit from having an FET. Sometimes, embryos are frozen to be donated to others, or for medical research.

paris, france   april 11  actress jennifer aniston attends the louis vuitton masters a collaboration with jeff koons dinner at musee du louvre on april 11, 2017 in paris, france  photo by marc piaseckiwireimage
Jennifer Aniston recently said that she wishes she’d frozen her eggsMarc Piasecki - Getty Images

The similarities between egg freezing and embryo freezing

Sandy Christiansen, embryologist and fertility coach at Bėa Fertility, explains the key similarities.

1) How the eggs/embryos are frozen and stored

“A key similarity is the way the eggs and embryos are frozen and stored. In both procedures, a process called cryopreservation is used. This involves replacing the water in the cell with a freezing solution called a cryoprotectant, to prevent water in the cells from crystallising. Next, the eggs or embryos are frozen using a ‘fast freezing’ process called vitrification, and stored in liquid nitrogen.

“When they’re ready to be used, an embryologist will thaw them, using those that have survived. In embryo freezing, a thawed embryo can be transferred directly to the womb. In egg freezing, the eggs that have survived will be injected with a partner or donor’s sperm for fertilisation, before being transferred to the womb.

“Following a law change in July of this year, eggs and embryos can be frozen and stored for use in treatment for any period up to a maximum of 55 years.”

2) Potential side effects of hormone stimulation

“In order to collect eggs for both egg freezing and embryo freezing, you will give yourself daily injections of stimulatory medications that encourage multiple follicles (the sacs in the ovaries that contain eggs) to grow. Once your follicles have reached a suitable size, you will take a ‘trigger’ injection, which matures the eggs ready for collection.

“It’s important to remember that this is an invasive procedure that can take its toll on your body. During the stimulation phase of this cycle, you may feel bloated, tired, and experience mood swings and headaches. It is also possible to experience bruising around the injection site.

“When your eggs are ready to be collected, you will attend the fertility clinic where a doctor will carefully aspirate the eggs from your ovaries under anaesthetic. Again, this can be sore after the procedure, and you may experience pain, such as abdominal cramping.

“The stimulation and egg collection process – and the potential side effects – are the same, whether you’re having your eggs or embryos frozen.”

The differences between egg freezing and embryo freezing

Jenny Saft, fertility expert and co-founder at Apryl, explains what stands them apart.

1) Consent and autonomy

“A key difference between embryo freezing and egg freezing is the issue of autonomy. Eggs can be frozen without needing to be fertilised first, which allows women to preserve their fertility independently and decide what eventually happens to their eggs.

“With embryo freezing, the embryos belong to two people. This means if you’ve used a partner or private donor’s sperm, they could withdraw consent for the embryos to be used at any time before they are transferred (this does not apply if you’ve used sperm from a donor bank). This means if your circumstances change – a relationship breaks up, for example – you could end up in a situation where you are unable to use the embryos you’ve frozen.”

2) Cost

“The exact cost of embryo freezing and egg freezing varies significantly from clinic to clinic – and will also vary depending on whether you eventually use the frozen samples, and how long they are in storage for.

“Typically, one embryo-freezing cycle at a fertility clinic – which involves egg collection, sperm preparation, fertilisation and storage for a year – will cost around £5,000. You will have to pay a recurring charge of around £350 per year for storage thereafter, and an additional fee of £1,500 to £2,000 for embryo transfer if you wish to use the embryos later on. So the whole process can cost anything between £7,000 to £8,000.

“By comparison, an egg-freezing cycle tends to cost around £3,800 in the UK, with an annual storage fee of up to £350 and additional fees for medication. Sometimes, it can take women two or three cycles to collect the number of eggs they want to freeze (there is no ‘perfect’ number, and the number of eggs you choose to freeze will depend on your age, ovarian reserves and reason for freezing).

“If you choose to fertilise the eggs and go for embryo transfer further down the line, this procedure can cost up to £5,000. So the whole process for egg freezing, thawing and transfer can cost anything up to £10,000, and sometimes more.”

The success rate for embryo freezing versus egg freezing

“Since we started the fast freezing method (vitrification), the outcome of frozen embryos has improved significantly and the success of frozen eggs has completely changed to become as good as the fresh ones,” says Dr Gorgy.

Christiansen explains, “The success rate between embryo freezing and egg freezing isn’t all that different.

“Egg freezing success rates vary by retrieval age and volume, with success rates declining as you get older. For example, if you get 20 eggs frozen when you’re 35, your chances of having at least one baby is 90 per cent, compared to just 51 per cent if you store the same number of eggs at age 40. However, it’s important to note that not that not all clinics will have the same results. It’s therefore important to speak to your clinic about their specific success rates, and to understand which treatments they are specialists in, before committing to any treatment.

“There’s also no guarantee that eggs or embryos will survive the freezing and thawing process. Over 95 per cent of embryos typically survive being frozen and thawed using vitrification. Eggs also have a very good freeze-thaw survival rate (around 90 per cent). Some women's eggs are more delicate than others, meaning fewer eggs survive the thawing process than expected, and the same applies to embryos. In both cases, there is no guarantee of a baby once the embryos are transferred.”

Fertility checks

Dr Gorgy recommends first booking in for a fertility check appointment if you're considering either egg or embryo freezing. During one of these initial appointments at his Fertility Academy, you will undergo an ultrasound scan for an assessment of the uterus, ovaries and fallopian tubes, as well as a blood test to determine your ovarian reserve (the number of eggs you have). You'll then be presented with a detailed written report explaining the findings and offering any recommendations.

"It helps to know your ovarian reserve," he explains, to enable you to decide whether you want to go down the freezing route. "It is always better to know about your fertility potential to plan your life based on facts rather than assumptions."

He recommends a fertility check for "any young woman who has decided to postpone starting a family for whatever reason" and "particularly those who have family history of premature menopause".

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