How to measure the cervical length

Cervical insufficiency ultrasound

The FMF England presents the following guidelines towards the proper measurement of the cervical length:

  • Empty bladder and dorsal lithotomy position.
  • No undue pressure on the cervix (longer cervix).
  • Median sagittal view of the cervix.
  • Calipers between the triangular area of echodensity at the external os and the V-shaped notch at the internal os.
  • Examination-time 2-3 minutes (shortest measurement).

The combination of cervical length and obstetric history can be used to predict spontaneous preterm birth. Calculators can be found here: FMF Calculators.

A normal cervix and a shortened cervix in comparison.


  • Celik E, To M, Gajewska K, Smith GC, Nicolaides KH; Fetal Medicine Foundation Second Trimester Screening Group. Cervical length and obstetric history predict spontaneous preterm birth: development and validation of a model to provide individualized risk assessment. Ultrasound Obstet Gynecol 2008;31:549-54.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.