Female
Egg Freezing and Storage
The Advisory Committee on Assisted Reproductive Technology (ACART) has given Fertility Associates the go ahead to offer full egg freezing services to New Zealand women. Around 1000 babies have been born worldwide following the freezing, thawing and subsequent fertilising of eggs. Most have been born in the past few years, so this is a new technology with limited follow-up of the children.
Fertility clinics have been freezing cells for some time. The freezing of sperm has been available since the 1950s and the first frozen embryo baby was born in 1983. However eggs have proven much more difficult to freeze and thaw. The human egg is the largest cell in the body and freezing has frequently caused damage to the delicate spindle on which the chromosomes are lined up during the maturing process that is necessary before fertilisation can occur. New technology with improved freezing solutions has allowed eggs to survive the freezing and thawing process in a more robust manner. Studies on the health of the children born following egg freezing have been reassuring thus far.
Egg freezing may be useful in a number of clinical scenarios, such as a woman who is about to undergo treatment for cancer that may cause her ovaries to fail, couples having IVF who have religious, moral or ethical objections to embryo freezing, where sperm is unable to be produced after the eggs have been collected in an IVF cycle or when a single woman wishes to store her eggs becuase her fertility is falling as she ages.
The process around egg freezing involves the same ovarian stimulation regime as those used in IVF. The eggs are collected, as for any egg pick-up (OPU), under sedating drugs and then frozen. When the woman wishes to use the eggs, they are thawed, the sperm is injected inside the eggs (ICSI) and the resulting embryos are placed in the woman’s uterus. If there are surplus embryos these are frozen. While the fertilisation rate per thawed egg injected is lower than with fresh eggs, the chances of a pregnancy are expected to be similar to that of a frozen and thawed embryo.
Ovarian Tissue Freezing and Storage
At the moment we can freeze and store small pieces of the ovary. There has now been one report of a human pregnancy following the storage, thawing and replacement of ovarian tissue.
Currently our clinic only has permission from the Advisory Committee on Assisted Reproductive Technology (ACART) to offer storage of frozen tissue. This tissue will not be thawed until techniques have been further developed and ethical approval obtained for its use. We do not know when or if this will occur.
Freezing of ovarian tissue is available to women aged 16 to 35 and who have a medical indication for this procedure, such as chemotherapy, radiotherapy or surgery, which has a significant chance of causing ovarian failure. The ovarian tissue is removed laparoscopically. Currently there is no public funding for the freezing and storage of ovarian tissue.
This technique may be used to help women at risk of losing ovarian function due to radiotherapy or chemotherapy as treatment for cancer.