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Abstracts & commentary
Althuisius and colleagues randomized 73 patients historically at-risk for incompetent cervix. Twenty-three had a cerclage placed at the end of the first trimester, and another 44 were followed with weekly transvaginal ultrasounds. Eighteen patients developed a short cervix (< 25 mm) before 27 weeks. Of these, 10 had a therapeutic cerclage and eight were randomized to an approach of watchful waiting. The prophylactic cerclage group had a preterm delivery rate of 13% (3/23). None of the 26 who had cervices larger than 25 mm had a preterm birth (PTB), and only one of the 10 patients with a short cervix (< 25 mm) having cerclages had a preterm birth (10%). These results contrast with a preterm birth rate of five of eight (62.5%) in patients with a short cervix who had no cerclage.
In effect, by waiting until the second trimester and performing cerclage in only those who had a short cervix, one could avert the need for this invasive procedure in about 60% of cases with, if anything, a better outcome (1:26 PTB vs 3/23 PTB). (Althuisius SM, et al. Am J Obstet Gynecol 2000;183:823-829; Rust O, et al. Am J Obstet Gynecol 2000;183:823-829.)
Comment by John c. Hobbins, MD
The cervix has been blamed for too many preterm births. Older texts suggest that the true incompetent cervix, one that is mechanically incapable of containing a pregnancy, occurs in one in 1000 pregnancies. Yet, it seems that prophylactic cerclage is performed at the drop of a scalpel, based on the concept that waiting until cervical shortening occurs is a gamble not worth taking.
Prophylactic cerclage is not without risk. Ruptured membranes, cervical tears, and preterm labor have been reported during and following cerclage. Interestingly, although the procedure seems to make empiric sense in patients with a suggestive history of cervical incompetence, its value has never been proven. None of the randomized trials in the literature has shown a benefit from prophylactic cerclage, and only one other study besides the Althuisius et al’s paper has shown a benefit of cerclage in patients with shortened cervices. This non-randomized trial from Rust and colleagues in England demonstrated an efficacious effect of cerclage in patients with extremely short cervices (< 1.5 mm at 24 weeks), reducing the incidence of birth before 32 weeks from 50% to 5%.
For the first time Althuisius et al’s study, despite its small numbers, along with Rust et al’s study suggest the efficacy of second trimester cerclage, as long as it is done in the right patients. The available literature, however, casts doubt on the wisdom of prophylactic early cerclage, except in exceptional cases.
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