Cervical Cerclage Health Article

Definition

A cervical cerclage is a minor surgical procedure in which the opening to the uterus (the cervix) is stitched closed in order to prevent a miscarriage or premature birth.

Purpose

Approximately 10% of pregnancies end in preterm delivery, defined as a delivery that occurs before week 37 of pregnancy (the average pregnancy lasts 40 weeks). Premature birth is a major cause of serious health problems in neonates (newborn babies), including respiratory distress, difficulty regulating body temperature, and infection. More than 85% of long-term disabilities in otherwise healthy babies and 75% of deaths among newborns occur as a result of preterm delivery.

A woman with an incompetent cervix is 3.3 times more likely to deliver prematurely. The cervix is the neck-shaped opening at the lower part of the uterus and is normally closed tight during pregnancy until the baby is ready to be delivered, at which point it expands (dilates) to roughly 4 in (10 cm) in diameter. An incompetent cervix is prone to dilating and/or effacing (shortening) prematurely during the second trimester. The growing fetus subsequently places too great a strain on the cervix, leading to miscarriage (loss before week 20 of pregnancy) or premature delivery (loss after week 20). Approximately 1% of women will be diagnosed with an incompetent cervix (one in 500–2,000 pregnancies). It is the cause of 25% of losses during the second trimester.

A doctor might recommend a cerclage be performed if a woman has one or more of the following risk factors:

• a previous preterm delivery
• previous trauma or surgery to the cervix
• early rupture of membranes ("breaking water")
• hormonal influences
• abnormalities of the uterus or cervix
• exposure as a fetus to diethylstilbestrol (DES), a synthetic hormone that was used in the mid-twentieth century to treat recurrent miscarriages

Demographics

Racial and socioeconomic factors influence a woman's risk of delivering prematurely: African-American women are at more risk (16–18%) than white women (7–9%); women under 18 and over 35 are also at greater risk. Less educated women are more likely to deliver prematurely. Smoking during pregnancy is associated with a 20–30% greater risk of delivering prematurely. Male fetuses are more likely to be born prematurely and have a higher rate of fetal death than female fetuses (a difference of 2.8–9.8%).

Description

Elective cervical cerclage is a minor surgical procedure that is generally performed between 12 and 14 weeks of pregnancy (at the beginning of the second trimester) before symptoms of premature labor begin. Emergent cerclages are those placed later in pregnancy when cervical changes have already begun.

The patient will usually receive regional (epidural or spinal) anesthesia during the procedure, although general anesthesia is sometimes used. Spinal anesthesia involves inserting a needle into a region between the vertebrae of the lower back and injecting numbing medications. An epidural is similar to a spinal except that a catheter is inserted so that numbing medications may be administered as needed. Some women experience a drop in blood pressure when a regional anesthetic is administered; this effect can be countered with fluids and/or medications.

While there are numerous techniques for performing cerclage, the McDonald and Shirodkar techniques are the most common. The McDonald cerclage involves stitching the cervix with a 0.2 in (5 mm) band of suture. The cerclage is placed high on the cervix when the lower part has already started to efface. The stitch is usually removed around week 37 of pregnancy. The classic Shirodkar procedure involves a permanent "purse-string" stitch around the cervix; because it will not be removed, a cesarean section will be necessary to deliver the baby. Most Shirodkar cerclages are now performed with a modified technique that allows the sutures to be later removed.

Some less common methods of cerclage include:

• Hefner (or Wurm) cerclage (usually reserved for later in pregnancy when there is little cervix to work with)
• abdominal cerclage (a permanent stitch performed through an abdominal incision instead of the vagina; reserved for when a vaginal cerclage has failed or is not possible)
• Lash cerclage (a permanent stitch performed before pregnancy because of trauma to the cervix or an anatomical abnormality)