In vitro fertilisation is an infertility treatment that takes the man’s sperm and the woman’s eggs and combines them in the laboratory so that several eggs are fertilised. The term ‘in vitro’ means in glass, but in vitro fertilisation actually takes place in the laboratory using high-grade plastic dishes and carefully controlled culture conditions.
In many cases, sperm collection is straightforward and needs no medical intervention or preparation. Some men who do not produce sperm in their ejaculate may require surgical sperm retrieval. In these cases, in vitro fertilisation is achieved by intracytoplasmic sperm injection (ICSI).
The woman’s uterus must be ready to receive the embryos produced by in vitro fertilisation and this requires time and hormone treatments. Different methods of in vitro fertilisation are available, but the standard procedure is to give the woman a hormone to suppress her normal menstrual cycle. This is usually started on day 3 of her period.
Follicle stimulating hormone is then given as an injection each day for about 12 days to stimulate the ovaries to produce many more than one egg. This stage of hormone treatment can cause ovarian hyperstimulation syndrome in some women. This can be avoided if lower levels of hormones are used.
Once ultrasound scans confirm that the ovaries contain plenty of egg follicles, another hormone is injected to help mature the eggs and egg collection can be arranged. This is done three hours after the male partner provides his sperm, so that it can be washed and spun at high speed, ready for the in vitro fertilisation process. Eggs are collected using a thin needle inserted through the wall of the vagina; women are sedated for this.
The process of in vitro fertilisation then takes place as the eggs are mixed with the sperm. Not all eggs will be fertilised in the next 20 hours or so, but quite a few will, and will start to develop into tiny embryos. When they are two to three days old, the highest quality embryos can be chosen for transfer into the woman’s uterus. Alternatively, it is also possible to wait until five to six days after in vitro fertilisation to see if any of the embryos form blastocysts. Blastocyst embryo transfer can lead to higher pregnancy rates. Some fertility clinics recommend assisted hatching (AH) to encourage the embryos to implant in the uterus.
The embryos or blastocysts are transferred into the uterus using a thin tube inserted through the cervix. The number of embryos transferred varies and depends on the regulations in the country where the in vitro fertilisation procedure takes place, and also on the woman’s age. A pregnancy test 14 days later confirms whether the IVF cycle has been successful.