exposure. Serial transvaginal ultrasound evaluations of the cervix after 16–20
weeks may be helpful.
Management. With sonographic demonstration for fetal normality, elective
cerclage placement at 13–14 weeks’ gestation. With sonographic evidence of
cervical insufficiency after ruling out labor and chorioamnionitis, possible
emergency or urgent cerclage.
Consider cerclage if cervical length <25 mm by vaginal sonography prior to
24 weeks and prior preterm birth at <34 weeks gestation.
McDonald cerclage places a removable suture in the cervix. The benefit is
that vaginal delivery can be allowed to take place, avoiding a cesarean.
Shirodkar cerclage utilizes a submucosal placement of the suture that is
buried beneath the mucosa and left in place. Cesarean delivery is performed at
term.
Cerclage removal should take place at 36–37 weeks, after fetal lung maturity
has taken place but before the usual onset of spontaneous labor that could
result in avulsion of the suture.