Dr. Jay Iams of the Ohio State University Wexner Medical Center has championed the use of cervical length to predict preterm delivery risks.
It is generally accepted that a transvaginal ultrasound cervical length that is > 25 mm is normal. Cervical length is only useful in the second trimester and is not highly predictive after 28 weeks. It is not useful in multiple gestations or after a cervical cerclage has been placed. Vaginal progesterone has been advocated for a cervix length < 20 mm prior to 24 weeks.
Dr. Iams has recently advocated cerclage in the mid-trimester, especially if the cervix length is progressively shortening, or is < 15 mm.
Austin Perinatal Associates recommends observation of cervical length only between 16 and 24 weeks, depending upon the patient’s personal medical history. Should significant cervical shortening be seen, a rescue or emergency-type of cerclage will be offered. Our recommendation will depend upon the actual appearance and gestational age, not just upon cervical length alone. For those who decline rescue cerclage because it is a risky procedure, vaginal progesterone and bed rest will be offered.