What are the indications for performing a transvaginal ultrasound in cases of suspected miscarriage?

Perform a transvaginal ultrasound scan in cases of suspected miscarriage when a woman presents with bleeding or other symptoms and signs of early pregnancy complications and has:

• pain,
• a pregnancy of 6 weeks' gestation or more,
• or a pregnancy of uncertain gestation.

This scan is offered to identify the location of the pregnancy and to determine whether there is a fetal pole and heartbeat, which are critical for diagnosing viability or miscarriage.

If a transvaginal ultrasound scan is unacceptable to the woman, a transabdominal ultrasound scan may be considered, although it has limitations.

Additionally, transvaginal ultrasound is used to measure crown–rump length or mean gestational sac diameter to aid diagnosis, with follow-up scans recommended if initial findings are inconclusive.