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Braided suture material used for cervical cerclage may be associated with poor neonatal outcomes, as well as increased rates of infection and inflammation in the vaginal microbiome, two small U.K. studies found.

There was a significantly increased risk of fetal death and preterm birth when using braided suture material for cervical cerclage (a procedure designed to reduce the risk of preterm birth) compared to monofilament (or nylon) sutures, reported , of Imperial College London in the U.K., and colleagues in a retrospective cohort study.

A smaller prospective study discovered that the braided suture was also associated with vaginal dysbiosis (or abnormal bacteria in the vaginal microbiome), localized inflammation and premature cervical remodeling -- which can lead to preterm birth.

Results of both studies were published in

Examining both types of sutures, the authors noted that the braided suture is comprised of a woven, mesh-like material akin to a shoelace.

"Braided suture material is commonly used in preference to monofilament for cervical cerclage, because it is assumed that braided suture provides a more secure cerclage that is less likely to slip or tear the cervix; however, this assumption is not evidence-based," Kindinger and colleagues wrote.

Moreover, 80% of surgeons in the U.K. were said to to monofilament sutures.

For the first study, researchers examined data from 671 women in five U.K. hospitals and found there was a 15% rate of intrauterine death among women receiving the braided suture compared to 5% among women with the mono-filament suture (P=0.0001). Rates of preterm birth were 28% versus 17%, respectively (P=0.0006).

While not involved with the research, , of University of Utah in Salt Lake City, characterized the findings as "novel and interesting" in an email to 番茄社区app, but noted that additional research is still needed in order for the results to change practice.

"These findings suggest that use of monofilament suture for cerclages may improve outcomes and decrease the odds of preterm birth and stillbirth in some cases," he said. "However, this hypotheses should be tested in appropriate trials before clinical adoption."

The authors agreed, adding that their findings have led to a prospective randomized controlled trial called , which is currently ongoing.

The authors then sought to measure the impact of each suture type on the composition of the vaginal microbiome. Their second study randomized 49 women to receive either the braided or monofilament suture for cervical cerclage. They measured the bacterial composition at various time points throughout the pregnancy. As early as 4 weeks post-suture insertion, there was a high prevalence of women in the braided suture group with a dysbiotic microbiome.

Among women with braided suture material, there was a reduction in the abundant Lactobacillus communities seen in normal, healthy women, as well as an increase in many pathogenic bacteria, including those associated with bacterial vaginosis. By contrast, the vaginal microbiome of women with the monofilament sutures maintained stable, abundant levels of Lactobacillus.

"These data have important implications for normal and abnormal pregnancy," said Silver. "Alterations in normal vaginal, cervical, intrauterine, and placental microbiomes may increase the odds of preterm birth, stillbirth, and other adverse pregnancy outcomes, even in the absence of cerclage."

Kindinger's team also examined the inflammatory response associated with each type of suture material. They found that only braided suture material was associated with an increased release of inflammatory cytokines in the cervicovaginal fluid.

Finally, they looked at potential cervical vascularization, which suggested women with braided suture material were undergoing a premature cervical remodeling -- leading to potential increased risk for preterm birth.

"The work that has been done trying to link infection and dysbiosis in pregnancy to poor outcomes has really been limited to animal studies and associative studies, so I think that's quite an important additional finding of this paper," said co-author , also of Imperial College London, in an interview. "This might have important implications in the longer-term health outcomes of the neonate – if we are inadvertently causing dysbiosis in pregnancy because of intervention."

Limitations to the study include the first study's retrospective nature, and the second study's small sample size.

The authors estimated that with two million cerclage procedures performed, hundreds of thousands of babies may be able to survive if a nylon suture was used.

"The available evidence we have is when performing cervical cerclage, nylon is the preferable material to use," Bennett added.

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