The goal of IVF is to achieve a healthy baby. This is done through efficient ovarian stimulation resulting in the collection of mature eggs that are fertilized creating embryos from which the best one or two can be selected for transfer.
Depending upon the response to ovarian stimulation and individual needs, many more eggs may be produced than are necessary to achieve a successful pregnancy. This can create concerns for those having IVF.
These concerns include:
1) Religious/moral issues limiting the number of embryos created;
2) Logistic reasons such as the inability to produce a semen sample the day of egg retrieval;
3) Legal issues such as separation pending divorce.
Cryopreservation or egg (oocyte) freezing offers a way to resolve these concerns. There are two general methods of accomplishing egg freezing . The conventional method involves slow freezing in which eggs are washed through different concentrations of cryoprotectant which replaces water in the cell protecting it from ice formation during freezing. A newer method called vitrification is a ultra rapid freezing method that is becoming the method of choice for oocytes because it is more efficient (more oocytes survive the procedure). Another reason why vitrification may be better is that pregnancy success rates using previously vitrified eggs approximate pregnancy rates using eggs that had not been previously frozen.