Any embryos which are not replaced can be
preserved and stored by freezing.
After placing the embryos in
ampoules or straws, the embryos are cooled in a controlled way so that they can
be stored in Liquid Nitrogen Refrigerators for subsequent use after
thawing.
Regulations about the storage intervals allowed for storage
of embryos and gametes vary around the world. Some have very short storage
intervals ( 1 year), others more lenient (10 years in the UK under some
circumstances) while other countries set no limits.
This animated sequence is taken from a video courtesy
of the Walsgrave Clinic, Coventry, UK. It is a loop sequence which will repeat
itself .