Freezing IVF Embryos

During IVF treatment, a woman takes ovulation-inducing drugs which spur her ovaries into developing mature eggs. These eggs are then removed from her ovaries, and put in a dish in a laboratory together with her partner's sperm. Hopefully, the sperm will fertilize the eggs, and then one or more of the resulting embryos will be available for transfer back to her uterus. Because of the increased risk of a multiple pregnancy, only a limited number of embryos can be ethically or legally transferred back into her uterus. However, sometimes more embryos are produced than can be used in this process. That's where embryo freezing, or cryopreservation, comes in.


This is a process used to preserve living tissue (i.e. cells) by cooling them to sub zero temperatures. Human sperm cells, eggs and embryos can all be preserved in this way, and stored for future use. When the cells are frozen, all their biological activity stops. In the case of human embryos, the freezing process takes two to six weeks. Sometimes the embryos don't survive the freezing stage, or indeed the thawing out process when the time comes for them to be used.

Why Do This?

There are a number of reasons why a couple might decide to freeze their excess embryos from IVF treatment. A few, but not all of these, are listed below:

Firstly, if they may look at cryopreservation as a back-up option should their current cycle of IVF treatment fail.

Secondly, aside from this additional reassurance in the short term, they might be thinking of the future - whether or not they might want more kids in a few years time, and if so, would they have trouble conceiving again?

Lastly, cryopreservation of embryos may be looked upon as a last chance to have family after receiving cancer treatment. Chemotherapy can cause permanent infertility in both men and women.


As with any new assisted reproduction technology, there are concerns about the possible risks to children born from embryos which have been frozen and stored. For example - could the cryopreservation process result in damaged embryos being implanted in a mother's uterus, thereby producing babies born with birth defects or later developmental and health-related problems?

Thus far, studies have found that babies born from frozen embryos do not have a higher tendency to experience such problems than babies born from non-frozen IVF embryos. Studies have also found that the length of time for which an embryo is stored has no bearing on the success any of pregnancy resulting from the implantation of that embryo. Experts agree, however, that more long-term monitoring of frozen embryo babies is required before definitive conclusions can be reached.

Ethical Considerations

Cryopreservation of embryos is a true ethical minefield. Those in favor argue that the embryo is a potential life, not an existing life, and that the benefits of this procedure in terms of human happiness and quality of life for couples outweigh all other considerations. Those who oppose this aspect of assisted reproductive technology view the embryo as an already existing life, which should not be manipulated by human hands in this way.

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