In a retrospective study about value of cerclage 160 patients with singleton pregnancies had been studied in two subgroups dependent from the moment of operative cervix closure and opposed a matched pair control group without cerclage. In both subgroups there is a more loaded obstetric history with reference to previous abortions. Preterm labour and premature rupture of membranes and tocolysis could be observed significantly more frequent in both subgroups than in the controls. Obstetric results are worse in the cerclage group with respect to birth weight, height and pregnancy duration, especially correlations between prognosis and opening of the womb at the moment of cerclage could be proved. Amniotic infection syndrome was three times more frequent in the cerclage group than in the controls. Contrary to the literature no increased frequency of cervical laceration or caesarean sections could be observed. In conclusion our results are contrary to the optimistic view on cerclage, important not only for indication, but also for instruction of patients before therapy.