[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Female genital tract](https://durgical.com/en/general-pathology/areas/female-genital/) › Ectopic pregnancy # Ectopic pregnancy - Lesion When an embryo implants outside the uterus, usually in the tube, the tube cannot stretch; it bursts and bleeds into the abdomen. Updated Nov 12, 2026 ## Key points - Sites: tube (most, mainly the ampulla), then ovary, abdomen, cervix, interstitial (cornual) portion and caesarean scar. - Risk factors: previous pelvic inflammatory disease and chronic salpingitis, previous ectopic pregnancy or tubal surgery, endometriosis and adhesions, assisted reproduction, smoking, pregnancy with an intrauterine device in place. - Morphology: villi and trophoblast in the tubal lumen and wall, haematosalpinx, blood clot; rupture of the wall. - Endometrium: decidualised stroma without villi; Arias-Stella reaction (enlarged, dark, atypical-looking glandular nuclei) from pregnancy hormones. - Rupture usually occurs early in the first trimester and causes acute abdominal pain and shock. ## What it is Ectopic pregnancy is implantation outside the endometrial cavity, and more than nine in ten occur in the fallopian tube. Anything that slows the embryo's passage, above all scarring from previous salpingitis, raises the risk. The trophoblast invades the thin tubal wall and its vessels, so the tube distends with blood and eventually ruptures, causing a hemoperitoneum that can be fatal. Meanwhile the endometrium becomes decidualised without villi, often with the Arias-Stella reaction. ## Structure - The tube is swollen, purple and filled with blood clot (haematosalpinx), with a rupture site in the wall. - Chorionic villi and implantation-site trophoblast invade the muscularis and vessels; an embryo may or may not be seen. - Tubal abortion: the pregnancy is extruded through the fimbriated end with bleeding into the pelvis. ## Step by step - Damage to tubal cilia and folds, usually from past infection, slows transport of the fertilised ovum. - The blastocyst implants in the tubal mucosa. - Without a decidua to limit it, the trophoblast invades deeply into the thin wall and its arteries. - Blood accumulates in the lumen and wall, distending the tube. - The tube ruptures, causing intraperitoneal haemorrhage, or the pregnancy is aborted through the fimbria. ## Clinical notes - Classic triad: amenorrhea, abdominal pain and vaginal bleeding; ruptured ectopic causes shock with hemoperitoneum. - hCG rises more slowly than normal and transvaginal ultrasound shows no intrauterine pregnancy at an hCG level at which one should be visible. - Ectopic pregnancy remains an important cause of maternal death in the first trimester. ## Memory aid A scarred tube is a narrow hallway: the embryo stops, digs into a thin wall, and the hallway bursts. ## Test yourself Think of the answer, then tap the question to see it. ## What is the most important risk factor for tubal ectopic pregnancy? Previous pelvic inflammatory disease with chronic salpingitis that has scarred the tube. ## What is the Arias-Stella reaction? Enlarged, hyperchromatic, atypical-looking nuclei in endometrial glands caused by pregnancy hormones; it occurs in normal and ectopic pregnancy and is not malignant. ## Why does a tubal pregnancy rupture? The tube has no decidua and a thin wall, so the trophoblast invades its vessels and the wall gives way as blood accumulates. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/general-pathology/ectopic-pregnancy/) [More Pathology questions →](https://durgical.com/en/practice/?f=pathology) ## Elsewhere in DurgiPedia - [Uterine tube](https://durgical.com/en/histology/uterine-tube/) - [Trophoblast and hCG; gestational trophoblastic disease](https://durgical.com/en/embryology/trophoblast-and-hcg-gestational-trophoblastic-disease/) - [The placenta and pregnancy hormones](https://durgical.com/en/physiology/the-placenta-and-pregnancy-hormones/) ## Connections ## Related 6 - [Pelvic inflammatory disease](https://durgical.com/en/general-pathology/pelvic-inflammatory-disease/) - [Diseases of the fallopian tube](https://durgical.com/en/general-pathology/diseases-of-the-fallopian-tube/) - [Spontaneous abortion](https://durgical.com/en/general-pathology/spontaneous-abortion/) - [Endometriosis and adenomyosis](https://durgical.com/en/general-pathology/endometriosis-and-adenomyosis/) - [Hemorrhage: petechiae, purpura, ecchymosis, hematoma, and what blood loss does](https://durgical.com/en/general-pathology/hemorrhage-petechiae-purpura-ecchymosis-hematoma-and-what-blood-loss-does/) - [Shock: types, stages and the organs it damages](https://durgical.com/en/general-pathology/shock-types-stages-and-the-organs-it-damages/) ## Related conditions 6 - [Ectopic pregnancy](https://durgical.com/en/conditions/ectopic-pregnancy/) - [Pelvic inflammatory disease](https://durgical.com/en/conditions/pelvic-inflammatory-disease/) - [Endometriosis](https://durgical.com/en/conditions/endometriosis/) - [Female infertility](https://durgical.com/en/conditions/female-infertility/) - [Chlamydia infection](https://durgical.com/en/conditions/chlamydia-infection/) - [Hypovolaemic shock](https://durgical.com/en/conditions/hypovolaemic-shock/) [← All of general pathology](https://durgical.com/en/general-pathology/) Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given. Sources: [Ectopic Pregnancy](https://www.ncbi.nlm.nih.gov/books/NBK539860/) (StatPearls (NCBI Bookshelf), 2026). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/general-pathology/ectopic-pregnancy/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/ectopic-pregnancy/