What is the definition or description of: Short cervix?

Ultrasound. doctors generally only look for a short cervix after a person has had a history of a preterm delivery. In the next pregnancy, doctor will perform transvaginal ultrasounds to look at the length of the cervix and if it drops below 1.5 to 2.5 cm, they may get concerned about a shortening cervix and offer treatment or closer observation for further shortening.