The first pregnancy from cryopreserved human embryos was reported in 1983. The freezing of embryos is now a routine procedure in most modern laboratories and thousands of IVF pregnancies have been achieved following freezing – thawing cycles.
This technique offers the couple two significant advantages:
The technique of cryopreservation of embryos takes about 2 hours and requires mainly special materials containing an amount of cryoprotective agents. The embryos are loaded into special tubes / sequins, the name and the specific code for each case is noted and then transfered to the laboratory. There are several protocols for the freezing process, all designed to safeguard the integrity of cells and the organelles inside them.
The cryopreserved substances help towards this direction, so the smallest possible losses occur after the thawing. Here it is important to stress that the embryos experience a great amount of stress when they are subjected to this process, a fact which sometimes leads to the loss of embryos. Typically, assisted hatching is performed on embryos originating from thawing, since the area surrounding the fetus is particularly hard and the fetus, as it develops, fails to hatch and be later implanted in the uterus.
It is worth noting that there is no evidence of an increased incidence of any defects in children, which are derived from freezing – thawing cycles and that embryos are born perfectly healthy. The time in which embryos could theoretically remain frozen is unlimited, by the law (Article 7.3/law 3305) provides that the maximum period of 5 years can be extended by another 5 years, following a written request signed by both spouses or sexual partners at the cryopreservation bank.