Videos Clips on DVD
- 15-1
Techniques for Performance of McDonald Cervical Cerclage
- 15-2
Robotic Abdominal Cerclage Placement
Cervical insufficiency is traditionally defined as structural weakness of the cervix leading to the inability of the cervix to sustain an intrauterine pregnancy. The incidence is highly variable depending on the criteria for diagnosis. Most cases are associated with congenital shortening, surgical amputation, or stromal damage secondary to unhealed lacerations. Risk factors for cervical insufficiency are depicted in Table 15-1 .
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Cervical Cerclage
The use of a surgical strategy to reduce the rate of previable or preterm birth dates to Shirodkar’s intervention with transplanted fascia lata using a homograft to improve cervical function. For decades, patients with repeated second-trimester losses have been candidates for history-indicated prophylactic cerclage when the mechanical strength of the tissue is presumed insufficient to resist protrusion of the uterine contents. Cervical performance reflects the tissue’s stromal characteristics to limit deformation forces until the appropriately timed onset of labor as well as the capability of the endocervical canal to resist migration of ascending microorganisms or other inflammatory mediators.
Unfortunately if this surgical intervention is limited to women with multiple second-trimester pregnancy losses as originally advanced by Shirodkar, few patients would benefit from a cerclage procedure. However, overly enthusiastic application of this surgical approach has led to unnecessary intervention and an inability to positively define its benefit. After several randomized trials have appropriately raised concern regarding the value of this surgical intervention to prevent preterm birth, evidence has affirmed the concept that contemporaneous findings in the index pregnancy can provide an evidence-based indication for cervical cerclage.
Case 1: Cervical Cerclage
A 28-year-old G3P2 is 20 weeks’ gestation. Her obstetric history is remarkable for a first pregnancy complicated by cervical insufficiency and intrauterine fetal demise. Cervical surveillance was performed in her second pregnancy and cerclage was offered when a transvaginal sonogram demonstrated an intact length of 2 cm after the application of fundal pressure for 20 seconds. Funneling to the level of the cerclage was seen after placement of the suture and she delivered preterm at 35 weeks’ gestation. A prophylactic intervention was offered for her third pregnancy.
When performed in well-selected patients with premature cervical shortening ( Fig. 15-1 ) and a history of preterm birth, cervical cerclage can improve outcomes. Following insertion of cervical cerclage, the cervix resumes normal length ( Fig. 15-2 ). Cervical cerclage has been shown to improve pregnancy outcomes in a well-designed phase III randomized trial. This trial was performed by the Maternal Fetal Medicine Unit of the National Institutes of Health (NIH) and had as its source population women undergoing cervical surveillance due to a history of prior preterm birth less than 34 weeks’ gestation. From this population of approximately 1000 women, the cohort with a cervical length less than 25 mm was offered randomization of surgical intervention or standard management (n = 302 women). Owen and colleagues documented that in the subpopulation of those with the shortest cervical lengths (<15 mm), cerclage significantly lowered the rate of preterm birth less than 35 weeks’ gestation, adjusted odds ratio 0.23 (0.08 to 0.66), which was the primary outcome. No other medical or surgical intervention for the prevention of preterm birth tested in a phase III trial has demonstrated such a remarkable benefit in either the study population or a subpopulation.
Despite such a remarkable finding in this subpopulation, when the intervention was assessed in all randomized cases with a cervical length less than 25 mm and a history of preterm birth, only a nonsignificant difference in the rate of early preterm birth was observed—32% versus 42%. An interaction was identified between the length of the cervix and the efficacy of the procedure for the primary outcome. Yet other secondary outcomes were significantly improved at the less than 25 mm cutoff, most important, perinatal death rates, potentially justifying the intervention at the 15- to 24-mm range.
The optimal surgical methodology for cervical cerclage also has been questioned and debated. The two most commonly used procedures, the McDonald and the Shirodkar cerclage, have been compared by several retrospective studies without identification of clear superiority. However, such comparisons are remarkably limited by sample size and a tendency not to investigate the clinical circumstance, which would allow differentiation in method to become discernible, and prospective trials are lacking. Given the absence of clear superiority, surgeons have justified their approach based on their comfort or training for the operation. However, several basic questions need to be asked. Is a Shirodkar cerclage with its need for more extensive cervical dissection the optimal approach for a woman with profound premature cervical shortening, marked thinning of the cervical stroma, and minimal substrate for dissection? Intuitively, the answer is no. Shirodkar developed his technique as an elective procedure prior to the onset of marked cervical change. In contrast, should women undergo a McDonald cerclage with minimal intravaginal cervix due to prior cervical procedures? Again, intuitively, the answer is no. No single procedure is optimal for all circumstances, and operators should be familiar with an array of procedures to best care for patients or make referrals to those with such understanding.
Indications for Cervical Cerclage
History-Indicated Cerclage
Cerclage is performed at approximately 12 to 14 weeks’ gestation for a history of multiple prior previable deliveries (original articles justified intervention with three or more such losses) characterized by painless cervical change. Well performed obstetrical history may allow for identification of candidates for the intervention compared with objective testing; however, generalizing the findings from trials that use subjective assessments alone as an indication for therapy may be limited due to confounding presence in other health care systems. Given the rarity of remarkable cervical change occurring prior to 14 weeks, these interventions have been appropriately described as prophylactic procedures.
Physical Exam–Indicated Cerclage
This cerclage is indicated at a previable gestational age regardless of obstetric history for women with visible fetal membranes and by necessity, some cervical dilation so long as chorioamnionitis is not identified. Observational studies and randomized trials have identified a reduction in mortality with cerclage in this setting. Amniocentesis with amnioreduction has been justified in this circumstance for both diagnostic and therapeutic purposes. Of note, intra-amniotic inflammation is not uncommonly observed in this population but intra-amniotic microbial seeding is less frequent. Intra-amniotic infection is a contraindication for proceeding with this surgical intervention. Given the exposure of the membranes to the external environment, these procedures have been termed as emergency or rescue operations. Although this terminology appropriately describes the severity of the circumstance, such terms should be reserved to an intact cervical length of near zero with visible membranes.
Ultrasound-Indicated Cerclage
In women with a history of preterm birth, transvaginal sonographic surveillance of cervical length can reduce the likelihood for recurrent preterm birth. Both medical and surgical interventions may be indicated for this population depending on the degree of premature cervical shortening. The exact cervical length cutoff to optimize outcomes and provide an indication for when to proceed with cerclage is unknown, but evidence suggests a benefit at less than 25 mm. Given that a treatment is being indicated for an ongoing depiction of cervical deformation with ultrasound-indicated cerclage, these procedures have been appropriately termed therapeutic cerclage.
Surgical Techniques of Cervical Cerclage
McDonald Cerclage
The McDonald cerclage was not the first procedure described to address the issue of cervical insufficiency; however, it is clearly the simplest intervention. The patient is positioned in dorsolithotomy and a weighted speculum is used to expose the cervix. The anterior and posterior lips of the cervix are grasped with sponge forceps or a tenaculum. The first point of introduction of the cerclage suture is important because the goal is to maximize postoperative cervical length, but not to enter the bladder, which can descend on the upper intravaginal portion of the cervix. The change in mucosal character from the smooth cervical surface to the folds of the vagina has been used as a safe demarcation site for initial placement of the stitch. However, a slightly more aggressive approach in most patients will place the first bite of the cerclage 3 to 5 mm distal to this interface depending on the individual anatomy.
Most operators use a 5-mm Mersilene tape (Ethicon, Inc., Somerville, NJ) and bury the material into the cervical stroma starting at the 12 o’clock position carrying it counterclockwise to the 10 o’clock position. Mersilene is the preferred material in the opinion of the author because it has a tendency to tear through the cervical stroma either at the time of cinching the knot or with the unfortunate complication of preterm labor. Using a pursestring-type stitch, the cervix is circumnavigated until the 12 o’clock position is again reached. Avoiding exit sites at the 9 o’clock and 3 o’clock positions is advantageous to avoid the cervical vasculature and unnecessary excess bleeding. The most important, and perhaps the most difficult, aspect of the operation is to maintain an optimal distance from the external os as the cervix is circumnavigated. The tendency, which should be avoided, is to lose residual cervical length particularly as the suture material is placed in and out of the posterior lip. The intravaginal segment of the posterior lip is typically shorter than the anterior lip. In addition, the redundancy of the mucosa is greater in the posterior fossa in part to accommodate the need for a change in cervical position that occurs with labor. Therefore, care is necessary to ensure a sufficient depth to the needle pass is obtained to reach the cervical stroma. Despite the apparent simplicity of the technique, performing the intervention well does require a thoughtful approach. See Figures 15-1 to 15-4 for ultrasound pictures of the cervix before and after placement of McDonald cerclage. (See the DVD for video demonstration of placement of McDonald cervical cerclage. 
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The procedure illustrated in the video is performed in a patient with a history of two preterm births. In this example, note that the Mersilene tape is reintroduced into the cervical stroma adjacent the exit point, so that the cervical mucosa can more easily heal over the mucosal defects, and thereby minimize access points for vaginal flora to enter the cervical stroma potentially soliciting an inflammatory response. Furthermore, the needle must be passed into the cervical stroma and not merely in the loose connective tissue plane between the cervical mucosa and cervical stroma. A cerclage that occupies the space between the cervical stroma and mucosa will regrettably “slide off” the end of the cervix when intracervical pressure increases.
Several complications from this intervention are possible and should be avoided if possible. The cerclage must not traverse the entire width of the cervical stroma and enter the endocervical canal. This complication enhances migration of microorganisms into the uterine cavity. If premature cervical shortening is already present, such a full-thickness needle-pass may also result in iatrogenic premature rupture of membranes (PROM). The delicate balance to reach a sufficient depth to ensure the suture is within the stroma versus too deep a stitch, which causes ruptured membranes, is a skill developed only with experience. Those with minimal experience should err on a shallower placement with compensation, if needed, in tying the knot more tightly. Remarkable tension is needed for tying any cerclage when Mersilene tape is used; however, undue force should not be used if the operator prefers monofilaments because this will slice the cervical tissue. After tying, the free ends of the tape are cut with sufficient tail to allow for easy identification at a future speculum examination to ease removal.
Several surgical adjuvants have been proposed to aid cerclage placement particularly when performing a rescue cerclage. Amnioreduction has been discussed. Other adjuvants include a Foley catheter balloon or cervical ripening balloon placed against the membranes and ultimately guided up into the endocervical canal into the lower uterine segment. This technique when combined with multiple ring forceps grasping the cervical edges may allow for membrane replacement and minimize damage to the chorion. Damage to the chorion, either prior to surgery by overdistention of the membranes into the distal vagina, or intraoperatively, by manipulation of the membrane during surgery, can be visualized as membrane splitting. Any such defect of the chorion is associated with an extremely poor prognosis. It is therefore important to inspect the membranes for evidence of structural integrity prior to proceeding with intrauterine replacement of prolapsed membranes and care should be used during any manipulation of the membranes.
Another adjuvant technique is bladder filling sufficient to “push” the fundus away from the cervix. The author has seen minimal success with such a strategy, and care should be taken not to overfill the bladder to cause bladder rupture/trauma. Finally, placing several gauze pads in the posterior fornix after the suture has been placed and pulling the cervix over this vaginal “ball valve” creates some ascent of the membranes prior to tying the cerclage suture and may reduce the frequency with which membranes prolapse past the level of the cerclage.
The postoperative management of the patient undergoing cerclage has been questioned. Should individuals undergoing this intervention undergo postoperative sonographic surveillance and what is the utility of this information? Migration of the membranes to the level of the cerclage has been associated with an increased risk for earlier preterm birth. Those patients in whom the membranes have reached or prolapsed past the level of the cerclage may be candidates for increased bedrest, but this adjuvant intervention has not been shown to improve outcomes by prospective trials. Other medicinal adjuvants such as the use of progestins, antibiotics, or antiinflammatory agents have not been adequately investigated by larger observational or randomized trials in these women at highest risk. Evidence from secondary analyses in those undergoing the NIH cerclage trial did not demonstrate benefit for adjuvant progestin treatment, but patient selection was not stratified by residual postoperative cervical status, and further evaluation is needed.
Removal of a McDonald cerclage is relatively easy as traction is placed on the intravaginal remnants of the suture and the loop is cut. This intervention can be performed in the office setting. The most serious longer-term complications of cervical cerclage result from cervical trauma when the cerclage suture is not removed in a timely manner despite the onset of labor. These complications include large cervical tears and fistula formation.
Modified Shirodkar Cerclage
The Shirodkar procedure was developed for women with the worst reproductive history. The Shirodkar procedure has a theoretic advantage because this methodology results in direct visualization of the cervical stroma, which is the target tissue, and the lack of exposure of suture material to vaginal flora. However, to achieve these ends the procedure requires far more cervical dissection than a McDonald approach.
For the Shirodkar cerclage, the initial surgical steps are with a scalpel. After appropriate positioning and prepping, a semilunar incision is made across the anterior cervical mucosa just proximal to the bladder. This anterior mucosa is dissected off the underlying stroma, and the bladder is pushed intra-abdominally. Displacing the bladder away from the external os provides the potential to increase the residual cervical length after the procedure as the knot can be placed higher. Furthermore, this dissection strategy also makes an intravaginal surgical approach feasible for women who have little remaining intravaginal cervix due to prior cervical surgery. When the cervix is flush with the apex of the vagina, the only options are for intra-abdominal approach or the use of this type of dissection. Unfortunately, if an imprecise anterior cervical incision is made or if prior surgery creates a problem with developing the surgical plane, the bladder can be entered. If this complication is encountered, it is most frequently repaired by a transvaginal two-layered closure and prolonged Foley placement. Once the anterior incision is performed, attention is turned to a similarly placed posterior semilunar incision that allows dissection of the posterior mucosa off the posterior cervical stroma. The result is a partially denuded cervix with exposure of the cervical stroma both anteriorly and posteriorly, which gives the operator direct access to the site of the tissue deficiency.
With the use of a curved Allis clamp, the lateral margins of the anterior and posterior cervical semilunar incisions are approximated on the right. A Mersilene tape is passed anterior to posterior through the cervical stroma medial to the clamp. I then prefer to take a small bite through the posterior cervical stroma as the needle is passed from the right lateral margin of the posterior incision to the opposite side to ensure the material is well anchored in stroma. In a similar manner, the Allis clamp is used to approximate the anterior and posterior cervical incisions on the opposite side. The needle and tape are passed from posterior to anterior through the stroma of the cervix, and again a small bite is made anteriorly to better imbed the suture material into the stroma. The knot is then tied tightly. The cervical incisions are closed with a running suture and the knot is buried beneath the mucosa if the operator desires to stay true to the original surgery.
However, one criticism with the Shirodkar procedure is the difficulty with removing the stitch if a vaginal delivery is pursued because these patients may require a repeat trip to the operating room to dissect free and incise the buried suture. One strategy to minimize this difficulty is to leave the distal tails of Mersilene past the knot exposed to the vagina during closure of the cervical incision allowing removal similar to the McDonald approach.
Despite the best surgical attempts, the transvaginal approach for cerclage placement has inherent limitations given the inability to access the upper cervix. For women with little intravaginal cervix, for those with extensive cervical lacerations, or those who have previously failed a transvaginal approach, an abdominal cerclage may be preferred.
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