What is an ectopic pregnancy, and what is a pregnancy of unknown location (PUL)?

An ectopic pregnancy is implantation of a blastocyst outside the uterine cavity - most commonly in the fallopian tube.

A pregnancy of unknown location (PUL) is a positive pregnancy test with no intrauterine or extrauterine pregnancy seen on ultrasound - it may be an early intrauterine pregnancy, a failing pregnancy, or an ectopic, and is followed up with serial beta-hCG.

Clinical relevance. Recognising a PUL as a possible ectopic ensures appropriate follow-up to avoid missing a life-threatening ectopic.

More Detail

Ectopic pregnancy and PUL

These are central concepts in early-pregnancy assessment.

Ectopic pregnancy

• Abnormal implantation of a blastocyst outside the uterine cavity.
• Incidence about 11.5 per 1000 pregnancies; it remains a cause of maternal death.
• Risk is increased by assisted reproduction (~1:100) and by tubal damage; heterotopic pregnancy (coexisting intrauterine + ectopic) is rare but more common after ART.

Pregnancy of unknown location (PUL)

• A positive pregnancy test with no pregnancy (intrauterine or extrauterine) visible on transvaginal ultrasound.
• It could be a very early intrauterine pregnancy, a failing/resolving pregnancy, or an ectopic.
• Managed by serial serum beta-hCG (and repeat ultrasound) to determine the outcome - any woman with a PUL is treated as a possible ectopic until resolved.