Final answer:
The ultrasound criteria for diagnosing a missed abortion include measurements and observations such as the absence of a heartbeat in an embryo larger than 7mm, a gestational sac over 25mm without an embryo, and lacking a heartbeat after a follow-up scan. Follow-up scans are critical for ensuring an accurate diagnosis.
Step-by-step explanation:
The term missed abortion? refers to a pregnancy loss where the fetus has died or does not develop but has not been expelled by the uterus. In terms of ultrasound (U/S) criteria, a few key indicators are checked to diagnose a missed abortion:
- An embryo larger than 7mm without a heartbeat.
- A gestational sac measuring 25mm or larger without an 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.
- No fetal heartbeat or movement in an embryo or fetus that has reached a size that is typically associated with such activity.
Follow-up is essential in the case where the U/S findings are uncertain, and additional scans may be scheduled to confirm the diagnosis.