Male fertility - it takes two to tango

The idea is to flood the tubes with active sperm so they are in a position to 'pounce' when the egg is released at ovulation. Only one sperm will actually penetrate the egg and fertilise it, but sperm hunt better in packs, so IUI is only likely to be successful if at least 1–2 million active sperm can be obtained. If sperm counts are very low, then it is possible to 'bank' sperm and freeze the samples until enough have been obtained. Success rates with IUI vary between 5% and 20% per cycle depending on the age of the woman and the severity of the male factor.

IVF (in vitro fertilisation)
Where sperm concentrations are very low then IVF will offer the best chance of achieving a pregnancy. The woman's ovaries are stimulated to produce 8–15 eggs with daily injections of the hormone FSH. When the ultrasound scans show that the eggs are likely to be mature, they're collected using a minor surgical procedure and placed in little glass dishes with specially prepared sperm. Fertilisation rates of about 60-70% can be obtained with IVF and two or three of the resulting embryos are transferred directly to the womb after a couple of days. Any spare embryos can be frozen for further attempts in the future. Typical success rates for IVF are 20–25%+ per embryo transfer for women under 38 years who respond normally to ovarian stimulation.

ICSI (intracytoplasmic sperm injection)
Where the sperm parameters are very poor (zero motility or low morphology) then the ICSI technique can be used to achieve fertilisation in vitro. In ICSI, the egg is fertilised by introducing a single immobilised sperm directly into the cell by using a fine hollow glass needle.