A Guide to Embryo Freezing (Cryopreservation)

Embryo freezing is a cornerstone of modern fertility treatment, providing crucial flexibility and increasing your chances of having a family from a single IVF cycle. It's a highly successful technique that allows you to preserve embryos for future use.

At Bridge Clinic, we use an advanced flash-freezing technique called vitrification, which ensures your embryos are preserved in the safest and most effective way possible, ready for when you need them.

What is Embryo Freezing?

Embryo freezing, or cryopreservation, is the process of preserving embryos (eggs that have been fertilised with sperm) by cooling them to very low temperatures. Once frozen, they are stored securely in our laboratory. When you are ready to use them, they can be thawed and transferred to the uterus in a Frozen Embryo Transfer (FET) cycle.

Why Freeze Embryos?

There are several important reasons why our specialists might recommend freezing your embryos:

• Preserving Surplus Embryos from an IVF Cycle: This is the most common reason. An IVF cycle often creates more than one high-quality embryo. After your fresh embryo transfer, any remaining suitable embryos can be frozen. This gives you the opportunity for another pregnancy in the future (e.g., for a sibling) without needing to go through another full cycle of hormone stimulation and egg retrieval.

• "Freeze-All" Cycles for Your Safety and Success: Sometimes, the best medical approach is to freeze all the embryos created in a cycle and not perform a fresh transfer. This may be recommended if:

  • There is a risk of Ovarian Hyperstimulation Syndrome (OHSS).

  • Your uterine lining isn't optimally prepared for implantation.

  • A "freeze-all" approach allows your body to return to its natural hormone state, which may create a more receptive environment for the embryo in a later FET cycle.

• Preimplantation Genetic Testing (PGT): If you are having your embryos genetically tested, they will be frozen after the biopsy while we await the results. A healthy embryo can then be transferred in a future FET cycle.

• Fertility Preservation: For couples or individuals who wish to preserve their future family-building options before one partner undergoes medical treatment (such as chemotherapy) that could affect their fertility.

The Embryo Freezing Process: Step-by-Step

The process begins with an IVF cycle and culminates in the secure storage of your embryos.

Step 1: Embryo Creation and Culture Your journey starts with an IVF or ICSI cycle. After fertilisation, your embryos are cared for in our laboratory's specialised incubators for 5 to 6 days until they reach the blastocyst stage. This advanced stage of development is crucial, as only strong, high-quality embryos are suitable for freezing.

Step 2: Vitrification (The Freezing Process) Our skilled embryologists use vitrification, a state-of-the-art flash-freezing method:

1. The embryo is carefully prepared by replacing the water within its cells with a protective solution (a cryoprotectant).

2. It is then cooled at an ultra-rapid rate, instantly turning it into a stable, glass-like state. This process prevents the formation of damaging ice crystals, which is why it leads to such high survival rates upon thawing.

Step 3: Secure Storage The vitrified embryos are placed in clearly labelled straws and stored in high-security liquid nitrogen tanks. These tanks are monitored 24/7 to ensure the temperature is constant and your embryos remain safe for as long as you need them.