Embryo Freezing

Freezing some or all the fertilized eggs, i.e. embryos, may be necessary in some cases. These conditions may be due to medical requirements or special reasons.

The most common cause of medical necessity is overexcitation of ovaries (ovarian hyperstimulation syndrome = OHSS) and is a condition where transfer might be detrimental to the patient’s health. Here, all the embryos are frozen and stored. Sometimes, in cases where good quality and large numbers of embryos are present, one or two embryos are transferred to the patient and the rest are frozen.

In this process, embryos are frozen by a method called vitrification using chemicals called cryoprotectants. They are stored in liquid nitrogen tanks at -196 C after freezing. Technically it is possible to freeze embryos in the 4-cell, 8-cell or blastocyst stage. Theoretically, embryos that can be kept for 10 years can be kept legally in our country for only 5 years. Legally, the couples must apply and sign each year to continue the storage of embryos frozen in the respective IVF center.