How would I know if I had an incompetent cervix?

Diagnosis with loss. Unfortunately most women don't know that they have an incompetent cervix until they experience a late miscarriage. Sometimes we discover cervical shortening on ultrasound that can clue us in before a loss occurs, but that is not typical.
Previous 2nd TM loss. An incompetent cervix is usually diagnosed after a second trimester loss where the cervix dilates before the onset of labor or contractions. Sometimes it is diagnosed during pregnancy by seeing shortening of the cervix or beaking of the membranes into the cervix on ultrasound.