To determine the predictive value of various cervical length measurements postcerclage for the outcome of preterm birth following both elective and rescue cerclage.

Materials and Methods
Over a five‐year period, we identified 59 women who had a transvaginal cerclage inserted followed by serial cervical length measurement. Of these, 18 were elective cerclages placed at 14 weeks of gestation on the basis of a history of cervical insufficiency and 41 were rescue cerclages performed at gestations ranging from 17 to 23 weeks following a diagnosis of shortened cervix on ultrasound. The women were asymptomatic throughout.

There was a strong correlation between cervical length postcerclage and gestation at delivery. For both groups, preterm birth could be predicted by the total cervical length. In the rescue cerclage group, the change in cervical length was predictive, with positive changes associated with later gestation at delivery. The presence of funnelling was predictive of preterm birth in the elective cerclage group only.

Transvaginal cervical length measurement is useful in the prediction of preterm birth postcerclage placement. Serial cervical length measurement postcerclage may assist with timely addition of interventions such, progesterone and antenatal cortico steroids for fetal lung maturation.