Oocyte vitrification or egg freezing is the process by which mature eggs or oocytes are collected from a woman’s ovaries and frozen for use at a later time to try for a pregnancy.

In order to have a suitable number of eggs to collect, fertility drugs are used to stimulate the ovaries to produce multiple eggs.  The developing follicles which contain the eggs can be seen on ultrasound scan.  They are monitored and when they are large enough, the eggs are removed from the ovary by a minor surgical procedure.  The eggs are frozen by a process known as vitrification i.e. by placing them in liquid nitrogen. When the woman subsequently wishes to use the eggs, they are warmed (thawed) and fertilized using ICSI (a type of IVF). If embryos develop, they are transferred, one or two at a time, to the woman’s uterus (womb).

The chance of having a baby under any circumstance is influenced by a number of factors including female age, previous pregnancy & births, duration of infertility (if applicable), fertility diagnosis, male fertility factors, the stage & quality of embryos transferred and the type of treatment used. These issues are also critical in deciding on the likely success of egg freezing.

As women age, it becomes increasingly difficult to get pregnant, carry a baby to full term and deliver a healthy baby.   At Merrion Fertility Clinic, we do not generally recommend egg freezing for subsequent use in women who are 38 years and older.

The success rates of egg freezing are improving all the time but they are still not as good as natural conception and also generally less than the success rates of IVF or ICSI using fresh eggs. So, while we recommend oocyte vitrification for those who have no other choice, natural attempts at pregnancy, followed by IVF/ICSI using fresh eggs if natural attempts fail are still superior to egg freezing.


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