In a study of almost 700 pregnant women who received a cervical stitch designed to prevent preterm labor, the use of one type of suture over another was associated with three times higher risk of stillbirth and almost twice the risk of preterm birth. The findings suggest that the suture may disrupt the vaginal microbiome and spur inflammation, one of the major risk factors for preterm birth. The results have helped launch a clinical trial in the UK reassessing the safety of the suture in women who undergo the procedure, known as cervical cerclage, which is performed about two million times annually. With common childhood diseases like diarrhea and measles now kept in check, preterm birth has emerged as the leading cause of death in children under five years old, claiming more than one million lives worldwide each year. Women with a weak or short cervix, often due to previous preterm labor or surgery for cervical cancer, are at risk of premature birth. A common preventative treatment is cervical cerclage, which sews the cervix closed to keep the baby inside longer during pregnancy. Two types of suture material--monofilament and multifilament braided--are used for the procedure. Evidence for one stitch being better than the other is lacking, but most surgeons prefer the braided suture because it's stronger and easier to work with. The suture material used may be critical because cervical cerclage can raise risk of vaginal infection, which is thought to cause preterm births. Previous studies have linked disruptions in the vaginal microbiome, the bacterial community residing in the vagina that plays a key role in reproductive health, to poor pregnancy outcomes, but until now have been limited to animal models or associative studies, according to David MacIntyre.
MacIntyre and colleagues now find that in 678 women in the UK, those who received cervical cerclage using the braided suture, compared to the monofilament suture, were three times more likely to experience nonviable births and almost two times more likely to undergo preterm labor. Further study revealed that the braided suture, perhaps because of its larger size or mesh-like structure, spurred the growth of diverse bacteria and stunted that of Lactobacillus species, which are important to maintaining a healthy vaginal microbiome. These perturbations were accompanied by an inflammatory response in women receiving the braided cerclage. In contrast, the monofilament cerclage had little impact on the vaginal microbiome or inflammation. Of the two million cervical cerclages performed each year, about 80% use the braided suture. The authors estimate that a switch from the braided to the monofilament suture used in cervical cerclages would prevent about 170,000 preterm births and 172,000 fetal losses each year worldwide. For further insights from MacIntyre and co-author Phillip Bennett, listen to the three related audio files at http://www.