aetiology

Last reviewed 01/2018

Male coital factors are implicated in 40% of cases. Causes include oligospermia, azoospermia, impotence, and anatomical abnormalities such as hypospadias - which prevents normal ejaculation of sperm into the upper vagina.

Peritoneal factors occur in 40% of cases, usually due to endometriosis. Recent evidence suggests that infertility in endometriosis may result from the presence of factors in the peritoneum that inhibit gamete function.

Abnormalities of the uterine cavity - such as Asherman's syndrome - are a rare cause of infertility. Uterine fibroids may cause infertility if sufficiently large to distort the uterine cavity or to block the interstitial parts of the tubes, but are more usually associated with spontaneous abortion.

Tubal blockage occurs in about 20% of cases. Fimbrial occlusion is the most common, and may be associated with prior salpingitis. Occlusion of the mid segment is usually due to tubal sterilisation; rarely, to tuberculosis. The isthmus may be occluded congenitally or from endometriosis.

Ovulatory dysfunction is evident in 15-20% of cases. Causes include anovular cycles, a poor luteal phase, oligo- menorrhoea and amenorrhoea.

Cervical hostility occurs in 5-10% of cases, due to either infection or female sperm antibodies.

Fertility may be impaired in poorly controlled diabetes.

Note:

• infertility is unexplained in 20% of cases
• multiple factors are present in 15% of cases