Embryos Freezing
Embryo freezing is popularly known as Embryo Cryopreservation.
It is the procedure of storing the unused embryos in liquid nitrogen for use in later treatment cycle.
Sometimes more embryos are produced in an IVF cycle than can be safely transferred to the uterus because of the risk of high order multiple births. When extra embryos are produced, they can often be saved using the cryopreservation process. In cryopreservation, embryos are gradually “passed through” special solutions lowering their temperature until they reach the cryopreserved stage (-196 F). When the embryos are ready for use in a future IVF cycles they are very carefully, gradually thawed. Embryos can remain frozen for many years and it is believed that there is no time limit.
Our assisted reproduction unit has a very successful embryo cryopreservation program.
The advantage of using cryopreserved embryos in future cycles is that it is not necessary to undergo ovulation induction with expensive medications (FSH) thus greatly lowering the cycle cost.
The female need only take medications to “synch” her body for embryo reception, using estrogen and progesterone to stimulate the endometrium and create a pregnancy like state.
Procedure of embryo freezing is very delicate and the main purpose is the removal of water without hurting the cell or egg. Once water has been removed, the cell is cooled at very low temperature which is around -0.3 C per minute until it has been fully frozen. On the other hand, vitrification is the newer method in which the journey of egg from the incubator to the nitrogen container is much faster than previous one. This faster method typically allows only one egg or embryo to work at a time and is placed in a highly concentrated cryoprotectant solution.
Embryo freezing procedure is somehow very complex and requires highly experienced embryologist. Not all unused embryos are stored, as most of them dead, only the strongest embryos are suitable for freezing.
IVF success rates using cryopreserved embryos are slightly less than fresh embryos but are still quite acceptable.
