Obstetrics and gynaecology for PRES Level 2

A 26-year-old woman presents with 7 weeks of amenorrhoea, left iliac fossa pain and light vaginal bleeding. She is haemodynamically stable. Serum beta-hCG is 2,400 IU/L and transvaginal ultrasound shows an empty uterus with a small amount of free fluid in the pouch of Douglas. What is the most likely diagnosis?

1. Ectopic pregnancy correct Correct. A beta-hCG above the discriminatory zone, around 1,500 to 2,000 IU/L for transvaginal scanning, with an empty uterus should be treated as an ectopic pregnancy until proven otherwise, and the free fluid raises the concern further.
2. Threatened miscarriage of an intrauterine pregnancy Wrong. That requires a visible intrauterine pregnancy with a closed cervix, and the uterus is empty.
3. Complete miscarriage Possible but less likely with this hCG level and ongoing pain. A complete miscarriage typically shows falling hCG and a genuinely empty uterus after documented products, and it does not explain unilateral pain with free fluid.
4. Very early intrauterine pregnancy not yet visible Unlikely above the discriminatory zone. It is the reason a pregnancy of unknown location is followed with serial hCG rather than dismissed, but it cannot be the working assumption when pain and free fluid are present.
5. Molar pregnancy Wrong. A molar pregnancy characteristically produces a very high hCG, often far above this, with a snowstorm appearance in the uterine cavity rather than an empty uterus.

The point: Empty uterus plus hCG above the discriminatory zone equals ectopic until excluded. Any woman of reproductive age with abdominal pain gets a pregnancy test. Management depends on stability, hCG level, mass size and fetal cardiac activity: expectant, methotrexate, or surgery.

Source: RCOG/NICE NG126 — Ectopic pregnancy and miscarriage: diagnosis and initial management NICE · tier 1, national regulator or guidance