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Pregnancy of Unknown Location

NICE Guideline [NG126] Ectopic pregnancy and miscarriage: diagnosis and initial management. Last updated: Aug 2023.

Background Information

Pregnancy of unknown location is defined by:
  • +ve Pregnancy test, BUT
  • TVUS Transvaginal ultrasoundcannot identify intrauterine / extrauterine pregnancy 

There are 3 main differential diagnoses to consider in pregnancy of unknown location:
  • Very early intrauterine pregnancy (that is not yet detectable by ultrasound)
  • Ectopic pregnancy
  • Miscarriage (with residual hCG)

Guidelines

NICE recommends placing more importance on clinical symptoms than serum hCG results, reviewing the woman's condition if any of her symptoms change, regardless of previous results and assessments.

Test of choice:
  • TWO serum hCG measurements taken at least 48 hours apart (but as near as possible)
  • Results are used to determine subsequent management
 

Offer TVUSTransvaginal ultrasound 7-14 days later (or earlier if hCG >1,500)
  • If viable intrauterine pregnancy confirmed → routine antenatal care
  • If viable intrauterine pregnancy NOT confirmed → immediate review by senior gynaecologist

 

Note this serial hCG result is suggestive of early intrauterine pregnancy but CANNOT exclude an ectopic pregnancy. Therefore, a follow-up TVUS is needed to differentiate between an intrauterine pregnancy and an ectopic pregnancy. 

Perform urine pregnancy test 14 days later
  • If -ve → no further action 
  • If +ve → return to Early Pregnancy Assessment Service within 24 hours 

Attend Early Pregnancy Assessment Service within 24 hours.

References

Author: Adams Lau
Reviewer:
Last edited: 27/04/25