For single embryo transfer (SET), it is very important that the best quality embryo is selected to be transferred.
It is equally important that, if any good quality embryos remain, they are frozen for use later. This may avoid the need for repeated drug stimulation, egg retrieval, sperm collection and fertilisation.
When embryos are frozen, every effort is made to ensure they are kept safely and securely:
Despite the precautions that are taken, not all embryos survive the freezing and thawing process. Occasionally, there may be no embryos that survive, although the chance of this happening is reduced by the embryologist selecting only good quality embryos for freezing.
Clinics have their own policies on freezing embryos, which should be discussed with you, this information is particularly important if you are likely to have a single embryo transfer. Some clinics may freeze a single good quality embryo, other clinics may have a policy that recommends you have a certain number of good quality embryos to freeze to give you the best chance of success.
If you are opting to have a single embryo transfer, you should discuss your clinic’s freezing policy with your clinician.
Embryologists usually assess embryos on the day of transfer and decide whether the embryos are suitable for freezing. The embryos are normally assessed by a grading system. Embryos that are at the correct stage of their development and are of good quality may be frozen.
"Selecting the best embryo when having a single embryo transfer is essential. To do this, embryologists assess embryo quality by using a grading system. To help select the best embryo, embryos can be cultured for up to 6 days."
Rachel Cutting, Association of Clinical Embryologists (ACE)
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