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 
• sac with no embryo and an MSD <12 mm on initial scan that fails to double in size on a scan ≥14 days later 
• sac with no embryo and an MSD ≥12 mm on initial scan with no embryo heart activity on a scan ≥7 days later 
• embryo (irrespective of crown-rump length) without cardiac activity on initial scan and a scan ≥7 days later

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)