Cervical cerclage is a procedure in which stitches are used to close the cervix—the lower part of the uterus that opens to the vagina--during pregnancy to help prevent premature birth or pregnancy loss. Before pregnancy, the cervix is closed and rigid, and during pregnancy, it gradually softens, effaces, and dilates in preparation for birth. An incompetent or weak cervix may begin to open too soon, before the baby can safely be born. 

Ideally, a history-indicated cervical cerclage is done between 12 and 16 weeks of pregnancy, but can be done up until 24 weeks of pregnancy. This procedure is typically avoided after 24 weeks due to the risk of rupturing the amniotic sac and triggering premature birth. The cerclage is usually removed at 37 weeks of gestation, when the baby is considered to be at term.