The ovarian hyperstimulation is preferably done by using a GnRH agonist rather than human chorionic gonadotrophin (hCG) for final oocyte maturation, since it decreases the risk of ovarian hyperstimulation syndrome with no evidence of a difference in live birth rate (in contrast to fresh cycles where usage of GnRH agonist has a lower live birth rate).
[4] Still, the amount of cryoprotectant used in the vitrification is crucial: too much is toxic for the embryo; but too little could cause the appearance of crystallised water, regardless of the speed at which the process is carried out.
In the open vitrification system, the sample has direct contact with liquid nitrogen, which allows ultra-fast freezing.
The world's first crossbred bovine embryo transfer calf under tropical conditions was produced by such technique on 23 June 1996 by Dr. Binoy S Vettical of Kerala Livestock Development Board, Mattupatti[5][6] World usage data is hard to come by but it was reported in a study of 23 countries that almost 42,000 frozen human embryo transfers were performed during 2001 in Europe.
[7] In current state of the art, early embryos having undergone cryopreservation implant at the same rate as equivalent fresh counterparts.
[2] The outcome from using cryopreserved embryos has uniformly been positive with no increase in birth defects or development abnormalities,[3][8] also between fresh versus frozen eggs used for intracytoplasmic sperm injection (ICSI).
[12] In addition, the duration of storage had no significant effect on clinical pregnancy, miscarriage, implantation, or live birth rate, whether from IVF or oocyte donation cycles.
[16] Doing so reduces the possibility of conceiving twins or triplets, thus allowing parents to exercise greater control over their vision for their families.
[23] For example, in Illinois, the courts employ at least two clear approaches to determining how embryos are allocated in the event of a divorce or separation of the parties.
For example, in Illinois, the Illinois Parentage Act of 2015 has contemplated situations in which parties, represented by independent legal counsel, enter into contractual agreements regarding the allocation of embryos, but no uniform statutory answer exists for situations in which parties failed to enter into such written agreements regarding allocation.