In obstetric and gynecological imaging, the cervical length is defined as the distance between the internal cervical os and the external cervical os.
Radiographic assessment
Ultrasound
- the cervical length is most accurately assessed on a transvaginal scan with an empty bladder
- in a normal gravid situation, the cervical length is considered to be at least 30 mm (3 cm)
- the presence of a full bladder can increase the cervical length particularly on a trans-abdominal scan