To Stitch or Not to Stitch — Cerclage for Preterm Birth
December 1, 2009 5 minutes read
To Stitch or Not to Stitch — Cerclage for Preterm Birth
Abstract & Commentary
By John C. Hobbins, MD, Professor and Chief of Obstetrics and Gynecology, University of Colorado Health Sciences Center, Denver, is Associate Editor for OB/GYN Clinical Alert.
Dr. Hobbins reports no financial relationship to this field of study.
Synopsis: Cerclage in patients with a very short cervix at 16-24 weeks and a history of preterm birth has been shown to be effective in decreasing the rate of birth up to 35 weeks of gestation.
Source: Owen J, et al. Multicenter randomized trial of cerclage for preterm birth in high-risk women with shortened midtrimester cervical length. Am J Obstet Gynecol 2009;201:375.e1-8.
Until recently, the literature has offered little direction on how to manage patients who have short cervices in the second trimester. However, help may now be found in the data from a long-awaited multicenter study, published in the latest issue of the American Journal of Obstetrics and Gynecology. This study seems to clarify whether cerclage has a beneficial effect on one type of patient — someone who has a history of preterm birth (PTB) and who now has a short cervix at 16-23 weeks of gestation.
Owen et al screened 1014 women who had a history of prior PTB (between 17 and 34 weeks) with cervical length (CL) exams by transvaginal sonography (TVS). The first scan was booked at 16 weeks, after which exams were performed at 2-week intervals until 24 weeks, unless the CL was between 2.5 cm and 2.9 cm, and then the interval was lowered to 1 week. Three hundred eighteen patients (31%) had CLs that were < 2.5 cm. After initial exclusions were applied, 308 were randomized either to having a McDonald cerclage or not. About 9% of each group wound up switching sides because of patient preference or mitigating clinical circumstances.
Thirty-two percent of women in the cerclage group had a PTB < 35 weeks vs 42% in the control group, a difference that did not attain statistical significance. However, there was a significant difference in a subgroup of 64 patients who had CLs of < 1.5 cm (odds ratio [OR], 0.23; 95% confidence interval [CI], 0.08-0.66). Although there was no difference between groups regarding delivery within 7 days, there was a significant decrease in pre-viable births and neonatal deaths in the cerclage group.
Commentary
To stitch or not to stitch — that has been the question since Shirodkar first introduced the concept of cerclage. Initially, the procedure was done in those whose history of silent preterm labor labeled them as having a cervix that was incapable of retaining a pregnancy. Then the patient population expanded to include those who had short cervices on digital examination or, later, diagnosed with TVS. Individual studies and meta-analyses up until 2001 showed no benefit of early (13-14 weeks) prophylactic cerclage in those with a history of PTB, or in those with short CLs.1-3 However, in that year Althuisius et al demonstrated in a randomized controlled trial (RCT) a benefit of cerclage in those with a history of PTB and cervices that shortened up until 24 weeks.4 In the same vein, a meta-analysis by Berghella et al suggested the benefit of following CL by TVS in patients with a history of PTB and intervening with a cerclage if the CL was < 2.5 cm.5 In this collection of pooled data, the incidence of PTB was 23% in the cerclage group vs 39% in the no-cerclage group (OR, 0.61; 95% CI, 0.42-0.92).
The Owen et al multicenter study seems to support the concept of intervening with cerclage if the cervix shortens in a patient with a history of PTB. However, the benefit was by far the greatest when the cervix was < 1.5 cm. If the statistically less compelling threshold of 2.5 cm were used as a criterion for cerclage, then this would represent one-third of the population with a history of PTB, compared with only 6.4% requiring cerclage if a more stringent CL cutoff of 1.5 cm were used.
Should all patients without a history of PTB, but who have short cervices, be considered for cerclage? No studies have shown benefit, including a subgroup in the Berghella meta-analysis above. Is there any benefit of cerclage in patients with twins who have short cervices? In a subset of one of the above studies, the incidence of PTB at < 35 weeks was two times higher in those with cerclage, compared with controls.5 So, the answer is no.
Is there a place for prophylactic cerclage at 13-14 weeks in those with a seemingly strong history of "cervical insufficiency"? No randomized trial has borne out this concept, and the Althuisius study demonstrated that this practice resulted in worse outcomes than if one simply followed CL between 20 and 24 weeks and acted only if the cervix shortened.4
Should an attempt be made to rule out intrauterine infection before placing a cerclage? One study has shown that 9% of completely asymptomatic patients with short CLs have evidence of an intra-amniotic infection,6 and a RCT from Japan showed that those with a short cervix and a positive cervical interleukin-8 (IL-8) who had cerclages had poorer outcomes than those who were simply observed, irrespective of whether they were positive for IL-8.7 This study indicated that inflammation and cervical manipulation (cerclage) are a bad combination, and underscores the importance of ruling out infection prior to putting in a stitch.
What has not been addressed is whether a less invasive approach, such as intramuscular or vaginal progesterone, would have the same effect compared with cerclage in patients with short cervices. However, this would need to be tested in a study with large numbers. It would not directly address one of the theories du jour that short cervices and preterm labor are linked because the distance that the troublesome bacteria in the vagina would have to travel to enter the uterus is diminished.
In summary, evolving data are now pointing toward performing serial CL exams between 16 and 24 weeks in singleton pregnancies with a history of prior PTB, and considering cerclage in those patients whose CL is < 1.5 cm and who have no evidence of intrauterine infection. Early prophylactic cerclage should be considered only in those with an extremely strong history of cervical insufficiency (two or more second trimester losses).
References
- Rush RW, et al. A randomized controlled trial of cervical cerclage in women at high risk of spontaneous preterm delivery. Br J Obstet Gynaecol 1984;91:724-730.
- MRC/RCOG Working Party on Cervical Cerclage. Final report of the Medical Research Council/Royal College of Obstetricians and Gynaecologists multicentre randomised trial of cervical cerclage. Br J Obstet Gynaecol 1993;100:516-523.
- Drakeley AJ, et al. Cervical cerclage for prevention of preterm delivery: Meta-analysis of randomized trials. Obstet Gynecol 2003;102:621-627.
- Althuisius SM, et al. Final results of the Cervical Incompetence Prevention Randomized Cerclage Trial (CIPRACT): Therapeutic cerclage with bed rest versus bed rest alone. Am J Obstet Gynecol 2001;185:1106-1112.
- Berghella V, et al. Cerclage for short cervix on ultrasound: Meta-analysis of trials using individual patient-level data. Obstet Gynecol 2005;106:181-189.
- Hassan S, et al. A sonographic short cervix as the only clinical manifestation of intra-amniotic infection. J Perinat Med 2006;34:13-19.
- Sakai M, et al. Evaluation of effectiveness of prophylactic cerclage of a short cervix according to interleukin-8 and cervical mucus. Am J Obstet Gynecol 2006;194:14-19.
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