Both are methods of fertility preservation that allow patients to use their healthy, young reproductive materials later on in life. During egg freezing, unfertilized eggs are frozen for use later. In embryo freezing, the eggs are fertilized to create embryos before they’re frozen.

Embryos can be frozen on any day starting from the day after it is fertilised until the 6th day of culture. We at our clinic prefer to fertilise on days 1, 3 and 5 (blastocyst stage).

The use of frozen embryos is easier psychologically and less costly. But the pregnancy rates for fresh embryos are better than frozen.

Embryo freezing begins with hormone medication, injected over for 8–12 days, that stimulates the ovaries to produce multiple eggs. Once mature, the eggs are collected from the ovaries via an egg retrieval procedure. Sperm from a male partner or sperm donor is prepared through a process called “sperm washing,” which isolates healthy sperm to improve the chances of fertilization. The sperm is then combined with the egg in the laboratory (known as in vitro fertilization) to create embryos. The embryos develop for approximately 5 days under close monitoring by embryologists, and finally, they’re vitrified (flash frozen). Just as with eggs, once frozen, embryos remain as healthy and high quality as they were when they were created.

Embryo freezing is more appropriate for people in long-term relationships or marriages, who know they want to have children together one day. Egg freezing offers more options and simpler choices for patients that are single or not ready to create embryos with their partner.

There was a time, using older slow freeze technology, when embryos survived the freezing and thawing process better than eggs, because embryos are slightly less delicate. However, the introduction of vitrification (flash freezing) has largely eliminated this difference. At Extend Fertility, the survival rates when freezing eggs vs. freezing embryos are very similar: 90% of eggs and 95% of embryos survive.