Embryo Freezing: Pros & Cons

Embryo freezing, also called cryopreservation, is a common part of modern IVF. It allows embryos to be stored for future use - whether that’s months or even years later. While the technology is well established, it’s not the right choice for everyone in every cycle. Here’s what to know.

How Embryo Freezing Works

Once your eggs have been retrieved and fertilised, your embryos are grown in the lab for a few days. At either the cleavage stage (day 3) or the blastocyst stage (day 5–6), any embryos not transferred fresh can be frozen using vitrification, an ultra-rapid freezing method that prevents ice crystals from forming.

Frozen embryos are stored in liquid nitrogen tanks at temperatures around –196°C until you’re ready for a frozen embryo transfer (FET).

The Pros of Embryo Freezing

1. Flexibility in Timing
You can delay your transfer to give your body time to recover after stimulation, or to fit around work, travel, or personal events.

2. Reduces OHSS Risk
If you’re at high risk for ovarian hyperstimulation syndrome, your clinic may recommend freezing all embryos and transferring later in a calmer hormonal environment.

3. Enables Genetic Testing
Preimplantation genetic testing (PGT) requires embryos to be frozen while results are processed, allowing time for careful decision-making.

4. Future Family Building
If you want more than one child, freezing embryos from the same cycle can give you a chance to have full siblings in the future.

5. Similar - or Better - Success Rates
Many clinics now see equal or even higher pregnancy rates with frozen transfers compared to fresh ones, especially in patients with high stimulation levels.

The Cons of Embryo Freezing

1. Delay in Transfer
If you were hoping for a fresh transfer, freezing means waiting another cycle (or longer) before your transfer.

2. Costs
Freezing and storage fees add to overall IVF expenses, with annual storage often billed separately.

3. Thawing Risks
Although vitrification is very effective, a small percentage of embryos may not survive the thawing process.

4. Emotional Impact
Knowing embryos are in storage can bring mixed feelings - hope, but also pressure and uncertainty about when (or whether) to use them.

5. Legal and Time Limits
In the UK, embryos can be stored for up to 55 years (with consent renewals), but decisions about long-term storage and disposal can be emotionally challenging.

When Freezing Makes Sense

Your clinic may recommend embryo freezing if:

• You have high hormone levels or OHSS risk after stimulation

• You’re doing PGT

• Your uterine lining isn’t ready for transfer

• You want to bank embryos for future family planning

• Life circumstances mean you need to delay treatment

Bottom Line

Embryo freezing has revolutionised IVF, offering flexibility, safety, and future options. But it’s still a medical and emotional decision — one that should be made with both your short-term and long-term goals in mind.