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Fertility Glossary

Implantation window

The limited time in each cycle when the lining is receptive to an embryo.

Frozen embryo transfer

Progesterone exposure opens the window of implantation, which is why transfer timing is linked to when progesterone starts or ovulation occurs.

Also known as: window of implantation, WOI

Related United Kingdom guides

Last reviewed: 23 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.

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