1ST TRIMESTER VIABILITY

Ultrasound

Findings diagnostic of pregnancy failure

• • crown-rump length (CRL) of ≥7 mm and no heartbeat on a transvaginal scan

  • mean sac diameter (MSD) of ≥25 mm and no embryo on a transvaginal scan

  • absence of embryo with heartbeat ≥2 weeks after a scan that showed a gestational sac without a yolk sac

  • absence of embryo with heartbeat ≥11 days after a scan that showed a gestational sac with a yolk sac

  • pregnancy with an embryo with no heart activity on initial scan and repeat scan ≥7 days later 2

  • sac with no embryo and an MSD <12 mm on initial scan that fails to double in size on a scan ≥14 days later 2

  • sac with no embryo and an MSD ≥12 mm on initial scan with no embryo heart activity on a scan ≥7 days later 2

  • embryo (irrespective of crown-rump length) without cardiac activity on initial scan and a scan ≥7 days later 2

Findings suspicious but not diagnostic of pregnancy failure

• • crown-rump length (CRL) of <7 mm and no heartbeat

  • mean sac diameter (MSD) of 16-24 mm and no embryo

  • absence of embryo with heartbeat 7-13 days after a scan that showed a gestational sac without a yolk sac

  • absence of embryo with heartbeat 7-10 days after a scan that showed a gestational sac with a yolk sac

  • absence of embryo ≥ 6 weeks after last menstrual period

  • amnion seen adjacent to yolk sac, with no visible embryo (empty amnion sign)

  • enlarged yolk sac (>7 mm)

  • small gestational sac in relation to the size of the embryo (<5 mm difference between mean sac diameter and crown-rump length)

  • large amniotic cavity (expanded amnion sign)

Practical points

When there are findings suspicious for pregnancy failure, follow-up ultrasonography at 7-14 days to assess the pregnancy for viability is generally appropriate.