Cervical incompetence is painless opening of the cervix that results in delivery of the baby between 16 and 22 weeks of pregnancy.
Normally, the cervix dilates only when labor starts, in response to contractions of the uterus. However, in some women, tissues of the cervix (the lower part of the uterus) are weak. When the growing fetus and placenta put pressure on the weak tissues, the cervix may open (dilate) long before the baby is due. As a result, the baby may be delivered too early. If cervical incompetence has occurred, the risk that it will recur in a subsequent pregnancy is probably less than 30%. The risk is higher for women who have had three or more miscarriages during the 2nd trimester.
The cervix may be weak because of a connective tissue disorder present at birth (congenital), such as Ehlers-Danlos syndrome, or because of an injury. For example, injuries may occur when a large piece of tissue is removed from the cervix for a biopsy or when instruments are used to dilate the cervix (as can occur during dilation and curettage, or D & C).
The following also increase the risk of having a weak cervix:
Diagnosis and Treatment
Cervical incompetence is not identified until a woman becomes pregnant. It is suspected when a woman has had previous miscarriages during the 2nd trimester. Findings during ultrasonography may also suggest cervical incompetence. For example, if ultrasonography shows that a woman has a short cervix, particularly a woman who is at risk of cervical incompetence, doctors may closely watch for signs of premature labor. Doctors can detect early dilation of the cervix when they do routine examinations during pregnancy.
Doctors can place stitches around or through the cervix to keep it closed. Sometimes they close the cervix with tape or wires. Such procedures are called cervical cerclage. Cervical cerclage is done if the risk of cervical incompetence is high, such as when a woman has had previous episodes. Before cervical cerclage, the woman is given a general or regional anesthetic. Then doctors usually insert instruments through the vagina to place the stitches. Stitches are usually removed before delivery. Occasionally, they are left in place, and cesarean delivery is done.
Last full review/revision December 2008 by Edmund F. Funai, MD