The Effect of Uterocervical Angle Changes on Prevention of Preterm Birth in Patients with Pessary

Back ground-Preterm birth due to cervical incompetence and short cervix is one of the most important debates in obstetrics .Beside the cerclage, insertion of pessary sometimes may help to continue pregnancy,but pessary sometimes can affect positively and occasionally may not affect positively and delivery was happened preterm.Material and Method : Our study was done on 65 mother with singleton pregnancy and between 22 -24 weeks of gestations ,all of them nulligravide ,with short cervical length (by transvaginal ultrasonography controlling),under 25mm ,that enrolled and were candidate for pessary (Hodge type), after giving consent form . we measured uterocervical angle (UCA) before and after pessary insertion .All the patient had 100mg progesterone support tranvaginally until 36 weeks .After observing, 40 cases had valuable degrees changes in UCA to narrow acute UCA with anterior attention , (toward pubic direction),or to acute narrow angle with posterior attention ,(toward sacral direction).The other 25 cases had not valuable angular changes after pessary insertion.Result: From patient with acute angle, 35 from 40 (87%)could reach above 34 weeks of gestations .from25 cases with no high UCA changes 15( 60%) cases could reach above 34 weeks.Conclusion: If pessary can change the direction of forces(pregnant uterus) from vaginal rout to pubis or sacral bone the heavy uterus flexed anteriorly or posteriorly , so this method can help keeping internal os, closed. Thus this is one of the mechanisms of successful pessary.