What is an incompetent cervix?

Cervical incompetence is the painless dilatation of the cervix, which typically occurs during the second or early third trimester of pregnancy. Membranes may "balloon" through the cervical opening, rupture of membranes follows and the immature and usually nonviable fetus is delivered.

This sad event will repeat with each pregnancy unless treated by placing a purse-string like suture through the cervix during the early part of the next pregnancy (cerclage).

The most commonly used procedure is known as the McDonald cerclage and it has remained the mainstay in the treatment of women with incompetent cervices. This procedure may be performed either electively (in the face of a past history or with known cervical shortening or change) or on an emergency basis (with evidence of early dilitation or "hour glassing of membranes). When comparing women with a similar history of cervical incompetence who were treated with bed rest or medications, women who have undergone cerclage have had more successful outcomes in the prolongation of pregnancy and neonatal survival.

Until fairly recently, a woman had to lose a baby in order to be diagnosed with incompetent cervix. Vaginal ultrasound now has the capability of defining changes to the cervix which may indicate early changes indicative of incompetence before fetal loss.

We often don't know why incompetence occurs in some women. Factors that have been associated with this are: cervical trauma (usually surgical; D&C, conization, cauterization), DES exposure in utero or abnormal cervical development, such as a short cervix or weak cervical connective tissue.

The true incidence of cervical incompetence is unknown; however, the risk of preterm labor rises four times after one preterm delivery, and approximately ten percent of preterm deliveries are caused by true cervical incompetence.

If your care provider identifies you as a client at high risk for cervical incompetence or if he or she notes shortening or premature changes to the cervix, vaginal ultrasound is performed. If there is a high degree of suspicion that incompetence may occur, an obstetrician or perinatologist would make a plan which may involve observation, bedrest and/or cerclage.

The cerclage procedure may be done in the operating room under general anesthesia, but more typically it is performed with local anesthesia. It may also be performed in outpatient surgical centers.

Upon arriving at some later gestational age (depending upon factors such as fetal maturity, condition of mother and condition of the cervix and suture), the suture is removed. The woman is monitored closely for several hours to see if labor ensues. If not, she may go home and await spontaneous labor.