Pregnancy of Unknown Location
NICE Guideline [NG126] Ectopic pregnancy and miscarriage: diagnosis and initial management. Last updated: Aug 2023.
Background Information
Definitions
Pregnancy of unknown location is defined by:
- +ve Pregnancy test, BUT
- TVUS cannot identify intrauterine / extrauterine pregnancy
Causes
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
Approach and Management
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
Increase >63% after 48 hours (early intrauterine pregnancy likely)
Offer TVUS 7-14 days later (or earlier if hCG >1,500)
- If viable intrauterine pregnancy is confirmed → routine antenatal care
- If viable intrauterine pregnancy is 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.
Decrease >50% after 48 hours (miscarriage likely)
Perform urine pregnancy test 14 days later
- If -ve → no further action
- If +ve → return to Early Pregnancy Assessment Service within 24 hours
Increase <63% or decrease <50% after 48 hours (ectopic pregnancy likely)
Attend Early Pregnancy Assessment Service within 24 hours