What is in vitro fertilization (IVF)?
In vitro fertilization (IVF) is the process used to conceive a child outside the body. A woman's eggs and a man's sperm are placed together in a plastic dish for fertilization. Once fertilized, the resulting embryos are placed back in the woman's uterus in the hope that a successful pregnancy will follow.
Ovulation induction agents, such as Pergonal are usually given to the mother 8-10 days before treatment, as they allow larger numbers of eggs to be recovered, improving the chances of a successful fertilization. Before the development of such drugs few eggs would be retrieved because it required careful monitoring of the mother's 'LH surge' in order to recover eggs at the right time. This also often resulted in the performing of egg retrievals in the early morning or night time because of the unpredictability of such an occurrence. As well as 'superovulation' inducing drugs, gonadotropin releasing hormone agonists carefully control the timing of retrieval by preventing any unexpected LH surges.
The eggs can be retrieved from the mother using the more common sonographic technique involving an ultra-sound guided needle piercing the vagina. The follicles of the woman are punctured and the woman's follicular fluid is removed and placed in an incubator. Laproscopic egg recovery involves retrieval through an incision in the abdomen. This is used in women who also require a simultaneous assessment of their pelvic anatomy through a diagnostic laparoscopy.
Semen is also taken from the husband. It can be analysed using 'sperm penetration assays', where some sperm is checked to see whether it can puncture a zone-stripped hamster egg. The sperm can also be cultured to detect bacteria which can reduce the chances of pregnancy.
The sperm and the egg are incubated together (at a ratio of about 75,000:1) in the culture media for about 18 hours. The eggs and sperm should fertilise in the usual way in this media, but if this is not possible, assisted fertilisation techniques -- such as injecting the sperm directly into the egg using intracytoplasmic sperm injection (ICSI) techniques -- may be used. They are then passed to a special growth medium and left for 40 hours until the eggs have become pre-embryos.
The fertilized eggs are transferred to the woman's uterus through a thin, plastic catheter, which passes through her vagina and cervical canal. Often, multiple embryos are passed in to the uterus to improve chances of successful pregnancy. If this procedure is unsuccessful, the mother has to be given one month for recovery before the IVF egg-extraction procedure is repeated. This may be avoided by freezing embryos in liquid nitrogen when they are fertilised, and transferring them during the natural ovulation cycle again.
The mother has to wait two weeks before she returns to the clinic for the pregnancy test. During this time she can boost the chances of pregnancy by continuing to take progesterone - which keeps the uterus lining thickened and suitable for implantation to occur. The chances of a successful pregnancy is approximately 20 per cent for each IVF cycle.
There is no clear evidence that infertility medicines, if properly used, increase the risk of birth defects or cancer. The increase in the hormone oestrogen can cause breast tenderness, slight nausea, dizziness and slight abdominal swelling. Occasionally, too many follicles develop and a condition called ovarian hyperstimulation syndrome (OHSS) may occur. This is an unpleasant experience, which may include marked abdominal swelling, nausea, vomiting and diarrhoea, lower abdominal pain and shortness of breath. There is also a theoretical risk (very rare) of damaging organs, or causing infection or bleeding, with the collection needle. |
