IVF: what you need to know

The procedure to collect the eggs takes about half an hour and can be done under a general anaesthetic, although many clinics prefer to use sedation and painkillers. A fine needle is passed through the back of the vagina and into the ovary. The fluid from each follicle is sucked into tubes and examined by the embryologists who look for eggs. Each portion of fluid is examined in turn until every possible egg has been collected.

In a woman who is at risk of overstimulation of the ovaries (eg because she has polycystic ovaries, or has experienced hyperstimulation syndrome before), fewer drugs are given and the eggs collected while still immature. The eggs are then allowed to mature in the laboratory. This technique, called in vitro maturation (IVM), is not yet available in all clinics.

The next stage is to put the sperm with the eggs. The semen needs to be produced shortly before the eggs are collected. The sperm are then washed and prepared and put with the eggs. The specialists can usually tell if fertilization has taken place after twenty four hours.

Replacing the eggs in the womb

If the eggs have fertilised and are developing normally, they will be put back into the womb two to three days later. The procedure is simple. A plastic tube is passed through the cervix (the neck of the womb) and the embryos put high into the womb.

To give the best chance of pregnancy, most IVF units put two embryos into the womb. This gives a better chance of a baby than transferring one embryo, but does give a chance of more than one baby developing. As the health risks for babies and mother are greater with a twin pregnancy, you may be advised to have only a single embryo transferred if you are under 35 years of age, have good embryo quality, few previous failed IVF cycles, and a good chance of conceiving this way. Your clinic will discuss these options with you.

Any healthy embryos that are not transferred can be frozen in liquid nitrogen for up to ten years but you must give your consent in writing for this.

About two weeks after the embryos have been put into your womb you can carry out a pregnancy test.