Cervical insufficiency describes the inability of the uterine cervix to retain a pregnancy in the absence of contractions or labor in the second trimester (1).
The exact mechanism underlying cervical insufficiency is unknown; however, surgical procedures for the eradication of cervical dysplasia (i.e., conization, loop electrosurgical excision procedures, trachelectomy) are thought to play a role (1).
The most commonly used definition for shortened cervix is a cervical length below the 10th percentile for a given gestational age. At 18 to 24 weeks of gestation, the 10th percentile is represented by a cervical length of 25 mm (2).
The use of vaginal progesterone is generally accepted medical management for patients with a short cervix and no history of previous preterm. In Europe, the use of the Arabin pessary has been popularized, and this device is still being studied in the United States. Pessary use is described in more detail in “Nonoperative Management” section.
The surgical treatment for cervical insufficiency is the placement of a cervical cerclage using either a transvaginal or transabdominal approach.
Traditionally, transvaginal cervical cerclage has been the first-line surgical treatment for cervical insufficiency. Although a number of techniques have been used, the two most commonly used are the McDonald and Shirodkar sutures.
Transvaginal cervicoisthmic cerclage (TVCIC) has been proposed as an alternative to transabdominal cerclage and involves a higher placement of the cerclage relative to the internal os (3). Further studies are needed to determine its efficacy.
Transabdominal cervical cerclage is usually offered in the following clinical scenarios:
At least one failed transvaginal cervical cerclage resulting in second-trimester pregnancy loss (excluding emergency or rescue cerclage placed because of painless cervical dilation and amniotic membrane prolapse into the vagina)
Anatomical limitations (e.g., after trachelectomy) (1)
The practice bulletin on the surgical management of cervical insufficiency from the American College of Obstetricians and Gynecologists (ACOG) divides the indications for cerclage into three categories based on history, physical examination, and ultrasonographic (US) findings with a history of prior preterm birth (PTB) (1) (see Table 2.4.1).
Prophylactic cerclage placement is not recommended in a twin pregnancy, given the lack of evidence supporting a decrease in PTB (1).
Emergency or rescue cerclage may be beneficial in twin pregnancy. When patients with a twin pregnancy who presented with painless cervical dilation on physical examination, and who were expectantly managed, were compared with a similar group of women who had received a transvaginal cerclage, the cerclage group were noted to have a lower PTB rate at 32 weeks (16.7 vs. 47.1%, p value [p] = 0.02), 34 weeks (35.2 vs. 76.5%, p = 0.009), and 36 weeks (61.1 vs. 100%, p = 0.002) (4).
Table 2.4.1 ACOG’s Practice Guidelines on Indications for Cervical Cerclage in Singleton Pregnancy
Pelvic examination is usually performed in the dorsal lithotomy position, using a speculum to visualize the cervix and vagina. Digital examination may be performed; however, careful consideration should be given to patients with cervical dilation and amniotic sac protrusion. Cervical insufficiency can be completely asymptomatic and may be diagnosed in the absence of any contractions or other signs (e.g., bleeding, infection, and/or ruptured membranes).
Other causes of preterm delivery include the following:
Intra-amniotic infection or inflammation
Daily vaginal progesterone is recommended in asymptomatic women with a singleton pregnancy, who have no history of PTB, and who have a short cervix measuring ≤20 mm before or at 24 weeks of gestation (1). The definition of short cervix is however not well established, and some clinicians use different cut-off values (15-25 mm).
A vaginal pessary may be considered in patients who have a short cervix and who are at risk of cervical insufficiency (1).
Activity restriction, bed rest, and pelvic rest have not been shown to be effective for the treatment of cervical insufficiency (1).
Serial transvaginal cervical length ultrasound, performed weekly or biweekly from 16 to 24 weeks of gestation, is recommended for women with a history of PTB at <34 weeks of gestation.
In our institution, cervical shortening is diagnosed when cervical length measured (from internal to external os) is ≤25 mm on transvaginal ultrasound before 24 weeks of gestation.
Patient evaluation for cervical insufficiency may also include tocodynamometry to rule out preterm labor after 20 weeks of gestation.
Additional workup may be indicated to rule out differential diagnoses including amniocentesis to rule out intrauterine infection or cervical cultures.
In this chapter, we will focus on preoperative planning, surgical management, and postoperative care of patients undergoing abdominal cerclage. Placement of abdominal cervical cerclage may occur pre- or postconceptionally.
We recommend performing abdominal cerclage (via laparotomy or laparoscopic/robotic) before 14 weeks of gestation. This procedure may be performed later in pregnancy; however, at that time, it may be technically more difficult and associated with a higher risk for complications.
When considering postconceptional placement of abdominal cerclage, it is essential to ensure fetal viability (ultrasound examination between 10 and 13 weeks of gestation) and to rule out genetic abnormalities if possible with noninvasive (NIPT) or invasive (chorionic villus sampling [CVS]) prenatal testing.
Contraindications to abdominal cerclage placement include the following:
Ruptured amniotic membranes
Any suspicion of intrauterine infection
Fetal anomalies incompatible with life
Suspected fetal chromosomal abnormality
Further discussion with the patient is needed to determine eligibility.
In cases of trachelectomy performed for early-stage cervical cancer in ongoing first and early second-trimester gestation, we recommend consideration of simultaneous abdominal cerclage.
Indications for placement of cervical cerclage (Figure 2.4.1) in singleton pregnancy are reviewed in Table 2.4.1.
The choice of suture material for cervical cerclage is still debated, and no single suture has been shown to be superior to any other (1).
Different suture types used for cerclage include the following:
Polypropylene suture is formed by propylene polymerization. The main distinguishing feature of this suture is the low coefficient of friction, making it ideal for cerclage (5) as it passes easily through tissue. This same feature, however, can make knots less secure.
Polyester suture is made from synthetic, braided, multifilament, polymerized, permanent material and is manufactured in coated and uncoated forms. Mersilene is the most common uncoated form used in obstetric practice. Polyester is nonabsorbable and retains its tensile strength indefinitely being second only to metal sutures in terms of tensile strength (6).
Despite the theoretical increased risk of infection with braided suture material, studies have failed to demonstrate any causal relationship between the type of suture material and adverse pregnancy outcomes (7). We favor 5-mm Mersilene tape for abdominal cervical cerclage, regardless of the approach.
Figure 2.4.1. Cerclage placement between the ascending and descending branches of the uterine arteries and the cervicouterine junction.
Abdominal cerclage via Pfannenstiel incision is performed with the patient in the dorsal supine position.
Laparoscopic/robotic abdominal cerclage is performed with the patient in the dorsal lithotomy position with Trendelenburg tilt.