Preterm birth, defined as delivery before 37 weeks of gestation, remains a significant concern in obstetric care. When premature delivery occurs due to a weakening and opening of the cervix, the condition is referred to as cervical insufficiency. This painless, early dilation of the uterine opening can lead to late miscarriage or spontaneous preterm birth. To mechanically reinforce the cervix and prolong the pregnancy, a surgical procedure called a cervical cerclage is often employed. The cerclage involves placing a strong suture, or stitch, around the cervix to keep it firmly closed under the increasing pressure of the growing pregnancy.
Defining the Procedure and Purpose
The cervix is the lower, cylindrical part of the uterus that normally remains long, firm, and closed throughout most of the pregnancy. The cerclage procedure functions by physically constricting the cervical canal, essentially acting as a structural barricade. A non-absorbable suture is placed high on the cervix and tightened like a drawstring to increase the tensile strength of the tissue. The primary goal of this mechanical support is to maintain the closure of the internal cervical opening. By doing so, the cerclage aims to extend the gestational period, ideally allowing the pregnancy to reach at least 34 weeks, which dramatically improves the newborn’s chances of survival and long-term health.
Indications and Types of Cerclage
A cerclage is not performed routinely and is instead recommended based on specific medical criteria determined before or during pregnancy.
Indications for Cerclage
The most common justification is a history-indicated cerclage, placed proactively (usually between 12 and 14 weeks) for women who have a history of second-trimester losses or preterm births linked to painless cervical dilation. This is a preventative measure based solely on past obstetric events.
A second indication is the ultrasound-indicated cerclage, offered to women with a prior spontaneous preterm birth who are found to have a short cervix (typically measuring less than 25 millimeters before 24 weeks of gestation). The third indication is the physical exam-indicated cerclage, sometimes called a rescue or emergency cerclage, which is placed when the cervix is already found to be dilated on physical examination in the mid-trimester, but before active labor or infection has set in.
Types of Cerclage
The type of cerclage used depends on the patient’s anatomy and medical history.
- The McDonald cerclage is the most common transvaginal approach, using a simple purse-string suture to cinch the outer portion of the cervix.
- The Shirodkar cerclage is also placed vaginally but involves a deeper stitch requiring the vaginal tissue to be moved aside, allowing the suture to be placed closer to the internal opening of the uterus.
- For women who have failed a vaginal cerclage or have significant anatomical issues, a Transabdominal Cerclage (TAC) is an alternative, where the stitch is placed higher on the cervix through an abdominal incision.
Measured Success Rates and Outcomes
The effectiveness of a cerclage is directly related to the indication for its placement and the gestational age at which it is performed.
For women receiving a history-indicated cerclage, the procedure has the highest success rate. Approximately 85% of these pregnancies result in delivery at late preterm or term gestation (34 weeks or later). This high success is attributed to the prophylactic nature of the procedure, as the stitch is placed before significant cervical changes occur.
Success rates remain high for women receiving an ultrasound-indicated cerclage, with roughly 75% of these pregnancies achieving a similar delivery outcome (34 weeks or later). The primary measure of efficacy is the prolongation of the pregnancy, often adding several weeks to the gestation period.
In the more urgent scenario of a physical exam-indicated cerclage, where the cervix has already begun to open, the success rate is lower but still significant. While a high percentage of these procedures may lead to a live birth, the mean gestational age at delivery is typically lower, often around 30 to 31 weeks. This outcome still provides a substantial benefit compared to expectant management. Transabdominal cerclage (TAC) is generally reserved for the highest-risk cases, such as those with prior failed vaginal cerclage, and is associated with very high success rates, often exceeding 90% in specific high-risk populations.
Post-Procedure Care and Potential Complications
Following cerclage placement, a brief period of recovery is necessary, and patients may experience mild cramping and light vaginal spotting for a few days. Post-procedure care focuses on minimizing strain on the stitch. Patients are typically advised to maintain pelvic rest (abstaining from sexual intercourse) and to avoid strenuous physical activities, heavy lifting, and long periods of standing.
Continuous monitoring is required, and patients are instructed to watch for specific warning signs, including persistent or heavy vaginal bleeding, foul-smelling discharge (indicating infection), or painful uterine contractions. Potential complications include chorioamnionitis (infection of the fetal membranes), premature rupture of membranes (PROM), and cervical trauma or laceration. The risk of these complications varies, with physical exam-indicated cerclage having a slightly higher incidence of infection or bleeding.
The cerclage stitch is typically removed between 36 and 37 weeks of gestation, when the pregnancy is considered late-term and the risks associated with preterm birth are significantly lower. Removal is usually a quick, straightforward outpatient procedure performed without anesthesia. If labor begins spontaneously before the scheduled removal, the cerclage must be removed immediately to prevent severe injury to the cervix and uterus as the baby descends.