Pregnancy of uncertain viability

Pregnancy of uncertain viability (PUV) is a term given to an intrauterine pregnancy in a situation where there are not enough criteria (usually on ultrasound grounds) to confidently categorise an intrauterine pregnancy as either viable, or a failed pregnancy

Ultrasound

Various authors have put forward definitions for a pregnancy to be categorised under this group (please refer to your local protocol/guidelines). Endovaginal/transvaginal ultrasound will show 1-3:

  • intrauterine gestational sac containing an embryo with CRL <7 mm with no fetal cardiac activity
  • gestational sac with MSD <25 mm containing no embryo

It is important that pregnancy failure is confirmed with absolute certainty, even in situations where it is thought highly likely, but does not meet the established criteria.

Recommendations for the most appropriate followup of a pregnancy of uncertain viability are evolving.  In a recent BMJ publication4, the authors suggest the following:

  • if MSD < 12mm with no embryo
    • rescan in 14 days.  
    • if MSD has not doubled and there is still no embryo - diagnosis of failed pregnancy can be made.
  • if MSD 12 - 25 mm with no embryo
    • rescan in 7 days
    • if no embryo with cardiac activity present - diagnosis of failed pregnancy can be made.
  • if CRL <7mm no heart beat
    • rescan in 7 days
    • if still no hearbeat with any size CRL - diagnosis of failed pregnancy can be made.

Although radiologists commonly use "viable" loosely in the first trimester to mean "living," in some settings, the term "viability" has a specific legal definition (see: failed pregnancy).

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Article information

rID: 21649
System: Obstetrics
Section: Gamuts
Tag: cases
Synonyms or Alternate Spellings:
  • Pregnancy of uncertain viability (PUV)
  • Intrauterine pregnancy of uncertain viability
  • Intrauterine pregnancy of uncertain viability (IPUV)

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