Cryopreservation is the term used to describe the process of freezing and storing sperm, eggs or surplus embryos from an in vitro fertilization cycle. There are 2 methods currently used for freezing in IVF labs-slow freezing and vitrification (ultra-rapid freezing)
Vitrification is the process of converting something into a solid without any crystal formation. This is done by adding a cryo-protectant. This is important because ice crystal formation can be very damaging to frozen embryos. Embryos can be frozen at the pronuclear stage (one cell), or at any stage after that up to and including the blastocyst stage (5-7 days after fertilization). Different cryoprotectants and freezing solutions and protocols are used for different stages of embryo development. Many IVF clinics freeze their embryos at the blastocyst stage
The most common reasons for doing IUI Procedure are a low sperm count or decreased sperm mobility. However it may be a treatment option in the following conditions as well:
Embryo cryopreservation allows use of embryos to be implanted at a later stage , this can be done to improve results as well avoid hyperstimulation. Also in event the couple wants to delay their fertility due to some reasons Embryos can be frozen and stored for later. Also the process secures against failure as the whole cycle need not be repeated again if the transfer fails and frozen embryos can be used for further attempts .The couple may choose to opt for another child using their frozen embryos.