Cervical incompetence is one of the main contributors to repeated pregnancy loss, accounting for approximately 25% of the cases. Typically it results in progressive cervical dilatation, leading to a painless second- or early-third-trimester abortion. In most instances cervical incompetence is the result of previous obstetric or gynecologic trauma; a congenital etiology is unusual. Despite the various reported diagnostic procedures, the obstetric history and frequent visual and digital examinations during pregnancy remain the most important factors in arriving at the correct diagnosis. In spite of the fact that numerous procedures have been advocated as treatment, the McDonald purse string closure technique is by far the most simple and effective corrective surgical technique, yielding an overwhelming number of successful pregnancies.
Ansari, Amir Hossein, and Robert A. Reynolds. "Cervical incompetence. A review." The Journal of reproductive medicine, vol. 32, no. 3, 1987, pp. 161-171.
Our goal was to study the effect of therapeutic McDonald cerclage on cervical length with the use of transvaginal ultrasonography. Cervical length was measured serially in singleton pregnancies in which there were doubts regarding cervical competence. When shortening of the cervix was substantial before 27 weeks' gestation a McDonald cerclage was applied. Wilcoxon signed rank test was used, and 1-tailed P <.05 was considered significant. In the 34 pregnancies studied, the mean cervical length measured at a mean gestational age of 14 weeks had decreased significantly (P <.0001) from 42 mm (95% confidence interval 38-47) to 21 mm (95% confidence interval 19-23) at a mean gestational age of 20 weeks 5 days, when a cerclage was applied. After the cerclage the mean cervical length increased significantly (P <.0001) to 34 mm (95% confidence interval 30-38) at a mean gestational age of 22 weeks 1 day (95% confidence interval 21 weeks 1 day-23 weeks 2 days). Therapeutic McDonald cerclage results in a longer cervical length as measured by transvaginal ultrasonography.
There are no absolute objective diagnostic criteria for cervical incompetence. Abdominal and endovaginal ultrasonographic assessment of endocervical length, both of which have been associated with technical problems, have been used to establish the diagnosis. Cervical cerclage may be useful in preventing silent cervical dilatation; however, no prospective trials with and without cerclage have been performed when endocervical shortening has been demonstrated by ultrasonography.
Fifty-one consecutive twin pregnancies studied prospectively were compared with 153 consecutive control twin gestations that were concurrently delivered, but chosen retrospectively. Study patients were managed by a protocol that used weekly ultrasound surveillance combined with clinical assessment. Control subjects were not managed by protocol or ultrasound surveillance. Seven of 51 study patients (13.7%) were diagnosed as having cervical incompetency before 30 weeks' gestation (range 18-28 weeks, mean 24). In comparison, 14 of 153 controls (9.2%) delivered before 30 weeks' gestation (range 18-29 weeks, mean 25). The mean cervical length, dilatation, and membrane herniation (funneling) at diagnosis were 1.9, 2.2, and 3.6 cm, respectively, for patients with cervical incompetency. There was a significant difference in perinatal mortality. All study twins survived, whereas nine control subjects delivered at a mean gestational age of 22.7 weeks, with a loss of 17 infants. Life table analysis demonstrated that a significantly greater proportion of controls delivered very low birth weight, premature twins. The use of ultrasound and clinical criteria to select patients for cerclage placement helped prevent birth of the youngest and smallest twins and significantly decreased perinatal mortality in the study group. Routine cerclage placement is not recommended for twin gestations, but multifetal gestations may benefit from ultrasound surveillance for cervical incompetency.