Overview of Cervical Insufficiency: Diagnosis, Etiologies, and Risk Factors.

The diagnosis of cervical insufficiency can be made in women with or without prior pregnancy losses. Cervical insufficiency has been defined by transvaginal ultrasound cervical length <25 mm before 24 weeks in women with prior pregnancy losses or preterm births at 14 to 36 weeks, or by cervical changes detected on physical examination before 24 weeks of gestation.