Abnormal gestational sac size is the most reliable indicator of abnormal outcome. The gestational sac should be 5-mm MSD by the fifth gestational week. Sonographic evidence is based upon demonstration of an abnormal embryo or gestational sac. Sonographic diagnosis of embryonic demise usually is made upon demonstration of an abnormal embryo. Sonographic evidence of an embryo lacking cardiac activity is the most specific indicator of embryonic demise.
Caution is advised in the diagnosis of embryonic demise.
Determination of whether the viewed structure is the embryo is critical, as no other morphologically recognizable structures other than a heartbeat exist at this stage of development. The embryo must be scanned thoroughly for evidence of a heartbeat. Most recommendations call for 2 independent examiners to view the embryo, either concurrent with the ED visit or at follow-up. Most sonographers recommend repeating the scan within 3-7 days to determine whether the embryo is developing normally. Apply endovaginal ultrasound whenever possible to limit image distortion due to patient habitus or an overdistended bladder.