IN the UK, the system is regulated and potential donors have to be carefully screened to make sure they are free of disease or congenital disabilities.

They have to be aged between 19 and 35 and are counselled to ensure they are aware of the step that they are taking. The donor's ovaries then have to be suppressed by daily nasal sprays or injections for about four weeks.

Her ovaries are then stimulated by daily injections for ten days, which can be painful and lead to weight gain and mood swings. The actual egg collection, sometimes called harvesting, is performed under a general anaesthetic.

The harvested eggs are then fertilised in the laboratory. The woman who will give birth is given hormone drugs to prepare her womb to receive the fertilised eggs. They are placed inside the womb and pregnancy follows.