Cervical insufficiency is painless opening of the cervix that results in delivery of the baby during the 2nd trimester (typically between 16 and 22 weeks) of pregnancy.
Connective tissue disorders that are present at birth and injuries can make tissues of the cervix weak.
When the cervix is weak, the baby may be delivered too early.
Cervical insufficiency is identified only after a woman becomes pregnant.
To prevent early delivery, doctors may stitch the cervix closed or prescribe a hormone to be inserted into the vagina.
Normally, the cervix (the lower part of the uterus) dilates only when labor starts, in response to contractions of the uterus. However, in some women, tissues of the cervix 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 insufficiency 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.
What causes the cervix to be weak is not well understood. Usually, no specific cause can be identified.
The following may increase the risk of having a weak cervix:
A connective tissue disorder present at birth (congenital), such as Ehlers-Danlos syndrome
An injury, as may occur when a large piece of tissue is removed from the cervix for a biopsy (called a cone biopsy) or when instruments are used to dilate the cervix (as can occur during dilation and curettage, or D & C)
Birth defects of the genital organs
A short cervix, detected during ultrasonography
Previous miscarriages during the 2nd trimester
Cervical insufficiency 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 insufficiency. For example, if ultrasonography shows that a woman has a short cervix, particularly a woman who is at risk of cervical insufficiency, doctors may closely watch for signs of premature labor. Doctors may also suspect cervical insufficiency if they 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. Such procedures are called cervical cerclage. Cervical cerclage is done if the risk of cervical insufficiency is high, as when a woman has had previous miscarriages during the 2nd trimester. 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.
If cervical insufficiency is confirmed, doctors may prescribe the female hormone progesterone, which is inserted into the vagina every night. This treatment can sometimes reduce the risk of a preterm delivery.