Cervical cerclage is not recognized as the usual treatment of threatened premature delivery including uterine contractions and cervical modifications. Pregnant women with a threatened premature delivery limited to the presence of a short cervix at digital examination or internal scan may however be offered therapeutic cerclage, different from prophylactic first trimester cervical cerclage, when cervical insufficiency is suspected. Studies on cervical cerclage to prevent premature delivery suffered a poor design and do not allow any strong definitive conclusion. In the presence of a shortened or dilated cervix at digital examination without uterine contractions, there is no strong scientific evidence to support the practice of therapeutic cervical cerclage. Conversely there is however no strong scientific evidence to reject this procedure especially in early pregnancy (before the end of the second trimester). Therefore therapeutic cervical cerclage remains a possible option only if premature labor, intrauterine infection or placental abruption have been ruled-out by a 48 hours inpatient bed rest. In patients without previous history of premature delivery or second trimester miscarriage, there is no scientific evidence to support therapeutic cervical cerclage in presence of a short cervix. Moreover, in this low-risk group cervical length ultrasound screening is not recommended. In patients with one or more previous premature deliveries or second trimester miscarriage but who do not reach Royal College criteria for prophylactic cervical cerclage, there is currently not enough evidence to support a policy of therapeutic cervical cerclage compared to bed rest. This latter recommendation may however depend on the severity of previous obstetrical history.