For conception to take place, a woman needs to ovulate, or release an egg from her ovaries. The egg enters the fallopian tube where it meets the sperm. A sperm cell penetrates the egg, a process known as fertilisation. The resulting embryo is transported down the tube to the womb where it implants into the womb lining (endometrium) a few days thereafter.

During in vitro fertilisation (IVF), ovulation stimulating drugs are taken to encourage a woman’s ovaries to produce more eggs than normal. Eggs are then removed and fertilised with sperm in the laboratory. A fertilised embryo is then placed into the woman’s womb (embryo transfer).

Problems with sperm, including a low sperm count, are very common. In these cases, success rates can be improved by using intracytoplasmic sperm injection (ICSI). This is where a single sperm is injected directly into the egg to fertilise it.