Failed early pregnancy

Failed early pregnancy refers to the death of the embryo and therefore, miscarriage. The most common cause of embryonic death is a chromosomal abnormality.

Radiographic features

Ultrasound

Findings diagnostic of pregnancy failure

• crown-rump length (CRL) of ≥7 mm and no heartbeat on a transvaginal scan ³
• mean sac diameter (MSD) of ≥25 mm and no embryo on a transvaginal scan ³
• 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
• 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 on repeat scan ≥7 days later ²
• cessation of a previously documented cardiac activity of embryo (irrespective of crown-rump length)

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
• absence of embryo when amnion seen adjacent to yolk sac (empty amnion sign)
• embryo present with amnion visible around it but no heartbeat (expanded amnion sign)
• small gestational sac in relation to the size of the embryo (<5 mm difference between mean sac diameter and crown-rump length)
• enlarged yolk sac (>7 mm)

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.

See also

• threatened miscarriage
• fetal death in utero