Cervical Cerclage (encerclage)- Cervical cerclage is performed as an attempt to prolong pregnancy in certain women who are at higher risk of preterm delivery. Cerclage placement may be indicated by a history of cervical insufficiency or by certain sonographic or physical exam findings in a current pregnancy. A cerclage is done in the second trimester of pregnancy to prevent preterm birth. Why is a cerclage placed? Sometimes the cervix isn't strong enough to stay closed as the pregnancy grows. This weakness is called cervical insufficiency (formerly called an incompetent cervix). The procedure is safe during pregnancy up to 24 weeks.