Ultrasound evaluation of successful rescue cerclage

INTRODUCTION: Cervical cerclage has been used for over 60 years for the treatment of cervical insufficiency for prevention of the preterm delivery. Over the ensuing years there has been however substantial controversy... [ view full abstract ]

INTRODUCTION: Cervical cerclage has been used for over 60 years for the treatment of cervical insufficiency for prevention of the preterm delivery. Over the ensuing years there has been however substantial controversy regarding selection criteria for this procedure and what the best approach to the patient with known or suspected cervical insufficiency would be. Several selection criteria such as patients’ history (more than 2 preterm births) and physical cervical evaluation have been applied during the past decades.
A short cervix on transvaginal ultrasound is known to be associated with an increased risk of preterm delivery. The addition of ultrasound evaluations of the cervix has been useful in selecting the patients with a history of a prior loss who would likely benefit from a cervical cerclage. There is no apparent benefit to cerclage in a patient with a short cervix alone who lacks a history of a prior preterm birth as most of these women with a short but closed cervix will deliver after 34 weeks. Randomized trials of cerclage for a short cervix alone have not consistently shown an increase in number of deliveries at term.
A rescue cerclage is one placed on an emergent basis in at a previable gestational age when cervical effacement and dilation occur in the absence of labor, abruption, or infection. A randomized trial of rescue cerclage is unlikely to be completed due to the scarcity and clinical heterogeneity of this patient population. However, several cohort studies suggest that rescue cerclage is a benefit to select patients in the clinical scenario of threatening preterm delivery prior to 24 weeks of gestation, with advanced cervical dilation and protrusion of the amniotic sac at or below the external os of the cervix. Severe funneling is seen on transvaginal ultrasound. The risk of delivery in the next 10-14 days is high in this setting with expectant management.
There is evidence that placing a rescue cerclage suture high in the cervix is more likely to be associated with successful pregnancy prolongation. Recently, the finding of a large (> 105 degree) utero-cervical angle (UCA) has been shown to significantly increase the likelihood of subsequent preterm delivery. This risk is synergistic with the findings of a short cervix and appears to markedly increase the risk of preterm delivery in the setting of a short cervix.

Therefore the aim of this study as a part ongoing quality improvement efforts was to evaluate ultrasound cervical parameters in patients, undergoing cerclage.
METHODS: We retrospectively reviewed the ultrasound information on several patients who presented with advanced cervical dilation prior to 24 weeks (N=7) and confirm that all had a UCA greater than 105 degrees. Rescue cerclage was performed in five patient who were felt to be good candidates and consented to surgery. Our protocol was to administer pre-operative antibiotics and post-operative indomethacin for 7 days post-surgery. A single prolene McDonald cerclage was placed as high as possible in the cervix. Intraoperative ultrasound was used to assess the adequacy of the cerclage placement with a successful stitch having the following characteristics. The anterior arm of the suture is less than 5 mm from the inferior edge of the bladder. The posterior arm of the cerclage is in the upper 1/3 of the posterior cervix. The postoperative cervix will have greater than 2 centimeters below the stitch and the prolapse of the membranes will be successfully reduced.
RESULTS: All 5 successful cerclages were found to restore the UCA to less than 95 degrees. Three patients have delivered and two pregnancies are ongoing. All three patients delivered at greater than 35 weeks with two out of three delivering at term. The mean increase in gestational age was 13 weeks following the stitch in these delivered patients.
CONCLUSIONS:
The use of intraoperative ultrasound has been shown to be beneficial. It provides immediate feedback on the location of the stitch and the degree of success at restoring the normal pelvic anatomic relationship. It appears that in addition to confirming that the stitch is high in the cervix, ultrasound can allow evaluation of the UCA which is helpful in quantifying the success of the cerclage at restoring the normal anatomic relationship between the cervical canal and the lower uterine segment.