Cryopreservation means preserving in a frozen condition. The
best known cryopreservation is for semen. If extra embryos are left after an
IVF / ICSI procedure they, too, can be frozen. Freezing spare embryos
allows multiple embryo transfers from a single egg collection and improves the
chance of live birth. Freezing is very cost effective, since transferring
frozen embryos is much less expensive than starting a new IVF treatment cycle.
Not all embryos are suitable for freezing. The embryos can be
frozen at the pronucleate, early cleavage or blastocyst stage. Overall about
50% of frozen embryos survive the thawing process.