Cervical length assessment scans
This is a transvaginal scan done to measure the length of the cervix.
It is recommended in women at high risk for preterm birth, including multiple pregnancies, those with a previous preterm birth, abnormalities of the uterus or previous cervical surgery.
This examination is usually carried out at the time of the anomaly scan but in women with previous preterm birth it may be necessary to perform a series of scans starting from 16 weeks.
A short cervix helps the obstetrician in deciding the need for a cervical stitch.