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An ectopic pregnancy occurs when the products of conception implant outside the endometrial cavity (1). 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%), in cervix, scar from a cesarean section or the abdominal cavity (0.1%) (1).
Non-tubal ectopic pregnancy is the term used to describe implantation of an embryo at a site lying outside the uterine cavity or fallopian tubes - there has been an increasing trend in the occurrence of these rare conditions, especially caesarean scar pregnancy (CSP) (2)
It is estimated that there are around 10,700 ectopic pregnancies in the UK each year, with an incidence of 11.1 in every 1000 pregnancies (3,4)
It is usually associated with a period of amenorrhoea followed by bleeding and pain.
A heterotrophic pregnancy is when an intrauterine and an extrauterine pregnancy occur together in a woman (5).
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 period or had abnormal vaginal bleeding."
Some women (around 8 to 31%) with suspected ectopic pregnancies may present without any signs of an extra- or intra-uterine pregnancy on initial transvaginal ultrasound scan (TVS). These women are categorized as having a pregnancy of unknown location (PUL).
Risk of ectopic pregnancy with different homornal contraceptivs: