Classically, it is characterized by painless cervical dilatation in the second trimester, with prolapse and ballooning of membranes into the vagina, preterm premature rupture of membranes (PPROM), followed by expulsion of an immature fetus. Unless effectively treated, this sequence may repeat in future pregnancies.
- Multiple studies have demonstrated that certain features of the cervix, primarily cervical length, when measured in the mid-second trimester, may predict preterm delivery. Cervical length less than 2.5-3 cm is considered as short cervix.
- Another feature termed funneling-ballooning of the membranes into a dilated internal os, but with a closed external os-has also been assessed.
- Etiology: Although the cause of cervical incompetence is obscure, previous trauma to the cervix--especially in the course of dilatation and curettage, conization, cauterization, or amputation-appears to be a factor in some cases. In other instances, abnormal cervical development, including that following exposure to diethylstilbestrol in utero, may play a role.
- The treatment of classical cervical incompetence is cerclage (os tightening). The operation is performed to surgically reinforce the weak Cervix by some type of purse-string suturing. Bleeding, uterine contraction, or ruptured membranes are usually contraindications to cerclage.
- Cerclage procedure: Two types of vaginal operations are commonly used during pregnancy. One is McDonald and the other is Shirodkar.
- Complications: PROM, uterine contractions and abortion may occur.
- The knot is usually cut at 37 weeks or any time before, if the patient goes in labor. If the knot is not cut, then during labor there can be cervical tears or rupture uterus.
- Benson and Durfee is an abdominal encerclage operation reserved in cases when previously vaginal operations have failed (abortion has occurred in spite of cerclage).