In order to prevent multiple Births and to prevent the complications related to twin pregnancy Fertility Specialists prefer using a single embryo to prevent multiple pregnancies and the rest are frozen and stored in case of future need. If the first round of Embryo transfer does not work then the frozen embryos from the first cycle of IVF are put to use by thawing them and using them in the second cycle of embryo transfer.

This process of freezing and thawing embryos to produce babies is the one of the greatest boon in assisted reproductive technology.

The process of freezing embryos has improved over time with vitrification - a fast freezing technology that has eliminated the formation of unwanted ice crystals which was seen in conventional freezing techniques. People opting for this procedure get equal results and even better results compared to fresh embryo transfer cycle.

The embryos are frozen in Cryo locks after stringent labelling and colour coding. These cryo locks are then placed in liquid nitrogen where they get stored until their need arises.
The freezing process takes several hours but the thawing of embryos is a short process.

There are several benefits of frozen embryo transfer:

1. Freezing the embryos offers the patients the option to undergo additional cycles of embryo trnsfer, without having to take medicines for stimulating ovulation. Patients avoid undergoing anesthesia again and again for egg retrieval process. Only preparation of the endometrium is done during the FET cycle. This saves time, expenses and physical stress.

2. Frozen embryo transfers are cheaper than fresh cycles as in case of the former, monitoring visits are reduced; there is no need for egg retrieval or embryo culture.

3. The progesterone level increases in a woman during ovarian stimulation and this may reduce pregnancy rates. This scenario is reduced with FET.

4. Frozen embryo can be tested for genetic defects prior to implantation.

5. Freezing embryos gives couples opportunity to plan for a second baby as these embryos can be used for up to a period of 5 years.