Fertility is the ability to conceive and become pregnant through normal sexual activity. Infertility may be defined as the failure to conceive after a year of regular intercourse without contraception. Fertility and reproductive medicine is involved with the diagnosis and treatment of diseases and disorders affecting reproductive ability, and also in procedures to assist reproduction. Some of the causes of infertility include: fallopian tube blockages (tubal infertility) or other tubal problems; endometriosis, a condition in which pieces of the endometrium, the tissue lining the uterus, is found outside the uterus and can affect the ovaries, uterus and nearby structures; unexplained infertility, where there is no identifiable cause; ovulatory disorders, in which an egg is not released from the ovary normally or regularly; low numbers of sperm in the male or other problems with sperm. Common procedures and treatments include in vitro fertilisation (IVF), in which sperm is placed with an unfertilised egg in a Petri dish to achieve fertilisation. The resulting embryo is then transferred into the uterus to begin a pregnancy or it is cryopreserved (frozen) for future use. To enhance the chances of fertilisation, especially in cases of low sperm count in males, a single sperm may be injected into each egg using a technique known as intracytoplasmic sperm injection. Donor insemination involves sperm collected from a screened donor being inseminated into a woman close to, or at the time of, ovulation. Intrauterine insemination may involve insemination with the partner’s sperm or the partner’s sperm being placed in the uterus just prior to ovulation. Ovulation induction involves the use of medication to assist ovulation in women who normally do not ovulate.