Is it better to freeze oocytes or embryos?

The conservation (or vitrification), whether oocyte or embryo, is done with liquid nitrogen at -196В°C and can last for years. What is the most effective method to ensure pregnancy? Here is what you need to know.

• The survival rate of an oocyte after thawing is much lower than that of an embryo;
• thawed oocytes can only be fertilized by the ICSI method, while fresh embryos can be fertilized independently in the laboratory or by the ICSI method (in case of male infertility);
• an oocyte does not necessarily ensure the formation of an embryo;
• in older women (but still of childbearing age), 5 to 9 vitrified oocytes (or more) are needed to produce at least one embryo on the fifth day of development;
• a genetic test cannot be performed on an oocyte, while the embryo can always be tested.

That said, if you decide to use a medically assisted reproduction technology for a fertility problem, it is always preferable to freeze the embryos rather than the eggs.