Single Best Answer (SBA) · Female Pelvic Anatomy
A 28-year-old has a tubal ectopic pregnancy. In which single part of the fallopian tube do most ectopic pregnancies implant?
Show answer and explanation
Answer: D. Ampulla
Parts of the fallopian tube and ectopic sites
| Part of fallopian tube (lateral to medial) | Note |
|---|---|
| Infundibulum (with fimbriae) | Open end near ovary |
| Ampulla | Widest part; commonest site of fertilisation and of ectopic pregnancy (~80%) |
| Isthmus | Narrow; ~12% of ectopics |
| Interstitial (intramural) | Within uterine wall; ~1 mm lumen |
Commonest ectopic site
- Over 95% of ectopic pregnancies are tubal.
- Of tubal ectopics, about 80% are in the ampulla, around 12% in the isthmus, and the remainder infundibular or interstitial.
Why the ampulla
- The ampulla is the widest part and the usual site of fertilisation, so a delayed or impeded conceptus tends to implant there.
Clinical note
- Interstitial (cornual) ectopics are rarer but dangerous because rupture can cause severe haemorrhage.
Other (non-tubal) ectopic sites include the ovary, broad ligament, uterus (cervix/scar) and peritoneal cavity.
Practise every Obstetrics & Gynaecology topic
This is a free sample. Sign up for the full bank of flashcards and exam-style questions on a spaced-repetition schedule, with 20 free stars a day.
More on Female Pelvic Anatomy
- FlashcardDescribe the structure and histology of the fallopian tubes.
- FlashcardWhat are the three muscle layers of the uterus?
- SBA questionA student is asked which structure attaches the ovary to the lateral angle (cornu) of the uterus. Which single…
- True/False MCQRegarding the cervix, which of the following statements are TRUE?