Could a belly ultrasound replace the internal one for preterm labor risk?

This study tested whether a noninvasive ultrasound done on the outside of the perineum (transperineal) can accurately measure cervical length in pregnant women, compared to the standard internal (endovaginal) method. Researchers enrolled 85 women in their second or third trimester who needed a cervical ultrasound. Each woman received both types of ultrasound by different operators, and the measurements were compared to see if the external method could reliably detect a short cervix, which is a risk factor for preterm labor.