An ectopic pregnancy occurs when the products of conception implant outside the endometrial cavity. The most common site is the fallopian tube - 17.4% in the fimbria, 55% in the ampulla, 25% in the isthmus and 2% in the interstitial portion. Less commonly, a pregnancy implants in the ovary - 0.5% - or abdominal cavity - 0.1%.

The condition occurs with an incidence of 1 in every 300 to 1000 deliveries in the UK.

It is usually associated with a period of amenorrhoea followed by bleeding and pain.

Note though that the advice from the CEMD report (1) states "it is essential that GPs and other clinicians, including staff in A and E departments, consider the diagnosis of ectopic pregnancy in any woman of reproductive age who complains of abdominal pain. It is important to recognise that the clinical presentation is not often "classical". BhCG (pregnancy) testing should be considered in any woman of reproductive age with unexplained abdominal pain whether or not she has missed a perior or had abnormal vaginal bleeding."