This is diagnosed when a couple has not achieved a pregnancy after one year of regular unprotected sexual intercourse (at least every 2–3 days) although about one half will conceive in the second year. Around 15–20 per cent of couples have difficulties in conceiving; in half of these cases the male partner is infertile, while the woman is infertile also in half; but in one-third of infertile couples both partners are affected. Couples should be investigated together as efficiently and quickly as possible to decrease the distress which is invariably associated with the diagnosis of infertility. In about 10–15 per cent of women suffering from infertility, ovulation is disturbed. Mostly they will have either irregular periods or no periods at all (see MENSTRUATION).

Checking a hormone profile in the woman's blood will help in the diagnosis of ovulatory disorders like polycystic ovaries, an early menopause, anorexia or other endocrine illnesses. Ovulation itself is best assessed by ultrasound scan at mid cycle or by a blood hormone progesterone level in the second half of the cycle.

The FALLOPIAN TUBES may be damaged or blocked in 20–30 per cent of infertile women. This is usually caused by previous pelvic infection, for example by CHLAMYDIA or by a condition such as ENDOMETRIOSIS, where menstrual blood is thought to flow backwards through the fallopian tubes into the pelvis and seed with cells from the lining of the uterus in the pelvis. This process often leads to scarring of the pelvic tissues; 5–10 per cent of infertility is associated with endometriosis.

LAPAROSCOPY may be required to assess the Fallopian tubes adequately, the ENDOSCOPE being inserted through the umbilicus under a general anaesthetic and a dye pushed through the tubes to assess whether they are still open.

In a few cases the mucus around the cervix may be hostile to the partner's sperm and therefore prevents fertilisation.

Defective production of sperm is responsible for up to a quarter of infertility cases. It may result from the failure of the TESTES to descend in early life, from infections of the testes, or from previous surgery for testicular torsion. Semen analysis can assess the numbers of sperm and their motility, and to check for abnormal forms.

In a few cases the genetic make-up of one partner does not allow the couple ever to achieve a pregnancy naturally.

In about 25 per cent of couples no obvious cause can be found for their infertility.

Ovulation may be induced with drugs.

In some cases, damaged Fallopian tubes may be repaired by tubal surgery. If the tubes are destroyed beyond repair, a pregnancy may be achieved with in vitro fertilisation.

ENDOMETRIOSIS may be treated either with drugs or with laser therapy, and pregnancy rates after both forms of treatment are between 40–50 per cent, depending on the severity of the disease.

Options for treating male-factor infertility include artificial insemination by husband or donor and, more recently, by in vitro fertilisation and INTRACYTOPLASMIC SPERM INJECTION. Following investigations, between 30 and 40 per cent of infertile couples will achieve a pregnancy usually within two years.

For women with unexplained infertility after 2 years of regular unprotected sexual intercourse, IN VITRO FERTILISATION (IVF) can be offered if available. For women in whom tests show hypothalamic-pituitary failure (see HYPOTHALAMUS) hormone treatment may be advised and for those with POLYCYSTIC OVARY SYNDROME ovulation might be stimulated by using drugs such as CLOMIPHENE and/or METFORMIN. (See ARTIFICIAL INSEMINATION; ASSISTED CONCEPTION.)