IVF (in vitro fertilisation)

This technique was originally developed to help women who had blocked fallopian tubes – however, it's now routinely used to treat sperm problems because it removes many of the barriers that sperm normally have to get through.

The woman takes hormonal drugs so that she produces several eggs – these are then collected on ovulation. The best sperm are selected, ie. those that are normally shaped and move well, and around 200,000 are placed next to the eggs. Embryos which successfully develop are put back in the womb (only a maximum of three can be replaced in the UK).