On an early ultrasound, it can be hard to distinguish an early pregnancy from a missed miscarriage when there's any confusion about the gestational age. To avoid misdiagnosis, doctors use specific guidelines to determine when ultrasound results may mean miscarriage.
In a report by the Society for Obstetrics and Gynecology of Canada, researchers recommended that miscarriage be diagnosed if a transvaginal ultrasound reveals the following:
- No heartbeat in an embryo larger than 5 mm
- Gestational sac is larger than 8mm and has no yolk sac
- Gestational sac is larger than 16mm and has no embryo
In addition, if an earlier ultrasound revealed a fetal heartbeat and a subsequent ultrasound finds no heartbeat, this definitely means a miscarriage. Falling hCG levels alongside an ultrasound showing an empty gestational sac or no fetal heartbeat may also lead to a miscarriage diagnosis.
Source:
Morin, Lucie and Michiel C. Van den Hof, "Ultrasound Evaluation of First Trimester Pregnancy Complications." SOGC Clinical Practice June 2005. Accessed 1 June 2008.
