Even when a human egg is fertilised by a sperm there is only a one in five chance of it developing into a baby. To have a successful conception and pregnancy can be likened, therefore, to being a pinball wizard, according to the Science Museum's exhibition, The Infertility Maze.
Problems with a man's reproductive system account for about 30 per cent of the causes of infertility. These include: Too few sperm, with a man producing less than 20 million sperm in each ejaculation, rather than the average of 120 million.
Poor quality sperm, which either cannot swim straight and fast to reach the egg, or are abnormal for other reasons.
No sperm at all, usually due to blocked tubes in the testes or hormonal problems.
The more common situation, however, is for the woman to have a fertility problem. These include: Failure to ovulate, accounting for at least 40 per cent of female infertility. This can be due to a number of reasons, including being under or over-weight, and hormonal imbalances.
Blocked fallopian tubes, which carry the unfertilised egg from the ovaries to the uterus.
Disease of the womb, such as benign tumours.
Poor cervical mucus, which blocks the entry of sperm to the uterus.
Endometriosis, where the lining of the womb grows outside the womb.
Recurrent miscarriage, sometimes because women produce abnormal embryos, or have some other hormonal problem.
The Science Museum has set up an infertility telephone inquiry service, operating between 1pm and 7pm from Monday to Friday on 0345 600444.
The Infertility Maze is open between 19 October and 26 February 1995.Reuse content