Why is vitrification used in embryo freezing?

The laboratory exposes the embryo to carefully controlled protective solutions, then cools it very quickly into a glass-like state. This limits the formation of ice crystals that could disrupt cells. The embryo is stored in a labelled cryogenic container. For a future transfer, the laboratory warms it gradually and removes the protective solutions before assessment. Embryos can respond differently to freezing and warming, so the treatment team should explain the laboratory's procedures and records.

Discuss which embryos are suitable for freezing, how they will be identified, how storage decisions are recorded and what preparation your uterus may need before transfer. Confirm how consent, storage instructions and contact details are kept up to date. Ask when the laboratory will tell you whether an embryo warmed appropriately. For the underlying method, see [Vitrification](/technology/vitrification/).

During medicines used to prepare for transfer, contact your clinic for severe pelvic pain, heavy bleeding, fever, faintness or breathing difficulty. Seek urgent help for sudden severe symptoms. The laboratory process itself is not something to adjust at home; report concerns to the fertility team using its urgent contact route.

Ask how embryos are assessed before freezing, what warming involves, how transfer timing is selected, and how storage and consent are managed if plans change.