Long-term storage of sperm is almost always possible before various types of medical treatment that can damage sperm production, for example, chemotherapy, irradiation therapy or surgery (including vasectomy). How the sperm are later used depends on the number and quality of the sperm before freezing and how well they survive freezing and thawing. It is often wise to store two or three samples if possible.
Beside storage of sperm for the above medical reasons, there may be social reasons, such as concern about ejaculatory performance at the time of treatment, or simply being out of town and apart from the woman at the time of ovulation. In the former instance, if a fresh sample cannot be produced on the day of treatment (such as for intrauterine insemination or IVF), the frozen sample can then be thawed and used as “back-up”. Because of the variability in sperm production, a satisfactory “back-up” might also be preferred if the sample on the day was likely to be inadequate. In the latter situation, the frozen sample is thawed when the woman is assessed as ovulating and then intrauterine insemination is undertaken at the appropriate time so that the chance of pregnancy is not lost.
The freezing of testicular tissue is recommended when testicular tissue is obtained for diagnostic purposes especially when it is necessary to know in an azoospermic male (no sperm in an ejaculate) whether the testis is even capable of producing sperm. An example of this would be a man with a suspected blocked or undeveloped vas deferens, or maldesceneded or malformed testis, provided, of course, that mature sperm are seen. Such sperm can then be extracted, when the tissue is subsequently thawed, and is fertile if injected into the egg – testicular sperm requires maturation in the vas deferens and seminal vesicles to be naturally fertile. The acronym for the obtaining of testicular sperm by aspiration is called TESA, or by biopsy is called TESE. Click here for more information on MESA PESA TESA.
The National Ethics Committee on Human Assisted Reproduction (NECAHR) has given Fertility Associates the go ahead to offer egg freezing to New Zealand women. Around 65 babies have been born worldwide following the freezing, thawing and subsequent fertilising of eggs so this is a new technology with limited long term data. Egg freezing is also available in Australia, Britain and the USA.
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 1993. 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 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 preserve her fertility.
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 egg injected is poor in comparison to other instances of ICSI, the chances of a pregnancy are expected to be similar to that of a frozen and thawed embryo.