Embryo Cryopreservation


The procedure of freezing and preserving embryos for future use is embryo cryopreservation. Embryos can be formed just for preservation or extra embryos extracted during IVF treatment can be preserved. At a later time, the embryos are thawed and used. Embryo cryopreservation is sometimes an important part of IVF programs.

Why embryo cryopreservation

A man or a woman might want to freeze and store their embryos for several reasons:

  • They may feel that it is a better choice than killing the extra embryos.
  • If the IVF process fails the first time it will provide another opportunity to get pregnant. There will be no need for the couple to go through egg pick up process again.
  • If the couples are able to have a child, they will be able to use the embryos later to have a second child.
  • Before starting treatments, such as for cancer, the woman can save embryos that could decrease or eliminate her chances of becoming pregnant.
  • In donor program, the embryos could be saved and given to someone else.
  • The embryos could be saved and donated for research.

Embryo Cryopreservation Process

A cell consists mostly of water. Ice forming in and between the cells is the main concern when freezing embryos. The cell wall can be hurt by ice crystals and may harm the small structures inside the cell.

In the freezing process, the embryo must be protected. This is done using cryoprotective agents called special fluids (CPAs). CPAs are like “anti-freeze” for cells.

Two different techniques are used by doctors to freeze and preserve embryos: slow programmable freezing and vitrification.

The embryos are frozen slowly, in stages, in the slow programmable freezing method. In rising strengths over 10 to 20 minutes, the CPAs are added to the embryos. Then the embryos are cooled in a machine that decreases the temperature minute by minute over two hours. When frozen at -321° Fahrenheit (-196.1° Celsius), the embryos are preserved in liquid nitrogen.

Vitrification is a form of rapid freezing that uses CPAs with far higher strengths. With this procedure, the doctor combines the CPAs with the embryos first. The cell can also be harmed by CPAs that are very strong. The embryos are immediately put in liquid nitrogen to avoid this. This phase transforms them into an almost solid state, like glass. Ice in incapable of getting formed in this state.

The embryos are slowly thawed when needed. To extract the CPAs, they are soaked in special fluids. Also, this restores the natural water balance of the cell.

How safe is embryo cryopreservation?

Study has shown that the baby is not affected by freezing and thawing embryos. There is no greater rate of birth defects or health complications for children born from frozen embryos than for children born from embryos that have not been frozen.

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