Cerclage suture linked with preterm birth
A study by British researchers suggests that cerclages done with braided sutures are more likely to end in preterm birth (PTB) or a nonviable pregnancy than are those done with monofilament sutures. The braided material, say the authors, appears to promote vaginal bacterial dysbiosis, which in turn results in local tissue inflammation and premature cervical remodeling.
Published in Science Translation Medicine, the findings are from a retrospective analysis and the researchers see an urgent need for clinical trials, powered for the outcomes of PTB, neonatal morbidity, and mortality, to assess the impact of cerclage suture material.
The authors assessed birth outcomes in a cohort of 678 women who received cervical cerclages at five UK university hospitals over a 10-year period. Half of the procedures were done with braided suture material and half with monofilament suture. The women in whom the braided suture was used had higher rates of nonviable births (delivery <24 weeks or intrauterine death) compared to those in whom the monofilament suture was used (15% versus 5%; P<0.0001). The braided suture also was associated with an increased rate of PTB at 24 to 37 weeks’ gestation: 28% versus 17% for monofilament; P<0.0001.
Although a history of PTB contributed significantly to the nonviable births, the researchers said the braided suture was the “primary driver” of that observed outcome irrespective of potential confounders including maternal age, ethnicity, and parity. It was also the major variable influencing risk of PTB, independent of maternal age, ethnicity, parity, and history of previous PTB. Distribution of cervical length was similar between the braided and monofilament suture groups.
The braided material, the authors found, caused a “marked shift toward dysbiosis” 4 weeks after cerclage and that change persisted until 16 weeks after the procedure. The material was also associated with an increasing proportion of women with reduced levels of Lactobacillus spp and increased diversity of anaerobic bacteria. In contrast, the women who had cerclages with monofilament suture maintained high levels of Lactobacillus spp, which remained stable. The researchers also noted that the braided material was associated with increased release of inflammatory cytokines—including interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor-α—into cervicovaginal fluid.
“We estimate that a global shift to monofilament suture use for cervical cerclage would prevent 170,000 PTBs [number needed to treat (NNT), 9.4; 95% confidence interval (CI), 5.9 to 22.6] and 172,000 fetal losses [NNT, 9.3; 95% CI, 6.6 t 16.0) per annum worldwide,” said the authors.