In order for a normal pregnancy to occur, an egg must be produced from the female ovary, adequate sperm must be released from the male testes, the sperm must reach the egg, fertilisation must occur and the fertilised egg must implant in the womb. If there is a problem in any of these steps, subfertility occurs.
Problems contributing to subfertility can broadly be due to defective egg release(ovulation problems),including Polycystic Ovarian Syndrome, defective sperm(male problems), tubal problems(sperm cannot meet egg), unexplained, implantation problems, endometriosis, fibroids, cervical and coital problems. The proportion of each type of subfertility varies in different populations. In 40% of couples, a problem will be found in both partners.