For women who are pregnant with one baby (a singleton pregnancy) and at risk for a preterm birth, when cerclage is compared with no treatment, there is a reduction in preterm birth and there may be a reduction in the number of babies who die (perinatal mortality) There is no evidence that cerclage is effective in a multiple gestation pregnancy for preventing preterm births and reducing perinatal deaths or neonatal morbidity. Various studies have been undertaken to investigate whether cervical cerclage is more effective when combined with other treatments, such as antibiotics or vaginal pessary, but the evidence remains uncertain.