Risk factors

Risk factors are recognized only in 25-50% of patients who receive a diagnosis of an ectopic pregnancy (1).

Predisposing factors for an ectopic pregnancy include:

• previous tubal surgery
• previous ectopic pregnancy
• previous induced abortion
• pelvic inflammatory disease (2)
• intrauterine contraceptive devices - although conception rarely occurs with an intrauterine device in place, 25 to 50% of such pregnancies are thought to be ectopic (3)
• tubal ligation
• assisted reproductive techniques – in women who underwent in vitro fertilisation:
  • the risk of ectopic pregnancy was increased even in women with normal fallopian tubes
  • the risk of heterotopic pregnancy is also increased to 1 case per 100 women from 1 case per 4000 women in the general population (3)
• history of sub-fertility - probably because it identifies a group of women with tubal problems (due to altered tubal integrity or function) (3)
• progestogen only, or mini, pill
• diethylstilboestrol exposure
• non-caucasian race
• hormonal factors:
  • induction of ovulation
  • delayed ovulation
  • ovum transmigration
• minor risk factors include:
  • history of cigarette smoking
  • women over 35 years
  • multiple sexual partners during the lifetime (3)

The risk of ectopic pregnancy increases with maternal age (2).

Notes:

• endometriosis and ectopic pregnancy
  • a retrospective large population-based study seems to question any role of endometriosis in the aetiology of ectopic pregnancy (2)
  • the study authors do however note that
    • "..mild endometriosis could have been missed during emergency surgery for a bleeding ectopic pregnancy unless it was specifically searched for. Moreover, as most operations were performed by laparotomy, it is likely that mild endometriosis was underdiagnosed due to hemoperitoneum.."

Reference:

• (1) The Association of Early Pregnancy Units (AEPU) 2007. Guidelines
• (2) Nybo Anderson AM et al. Maternal age and fetal loss: population based register linkage study. BMJ 2000; 320: 1708-12.
• (3) Barnhart KT. Clinical practice. Ectopic pregnancy. N Engl J Med. 200923;361(4):379-87
• (4) Bogdanskiene G et al. Association between ectopic pregnancy and pelvic endometriosis. Int J Gynaecol Obstet. 2006 Feb;92(2):157-8