Prospective observational study of vaginal microbiota pre‐ and post‐rescue cervical cerclage

Objective To investigate the relation between vaginal microbiota composition and outcome of rescue cervical cerclage. Design Prospective observational study. Setting Queen Charlotte's and Chelsea Hospital, London. Population Twenty singleton pregnancies undergoing a rescue cervical cerclage. Methods Vaginal microbiota composition was analysed in women presenting with a dilated cervix and exposed fetal membranes before and 10 days following rescue cervical cerclage and was correlated with clinical outcomes. Main outcome measures Composition of vaginal bacteria was characterised by culture‐independent next generation sequencing. Successful cerclage was defined as that resulting in the birth of a neonate discharged from hospital without morbidity. Unsuccessful cerclage was defined as procedures culminating in miscarriage, intrauterine death, neonatal death or significant neonatal morbidity. Results Reduced Lactobacillus spp. relative abundance was observed in 40% of cases prior to rescue cerclage compared with 10% of gestation age‐matched controls (8/20, 40% versus 3/30, 10%, P = 0.017). Gardnerella vaginalis was over‐represented in women presenting with symptoms (3/7, 43% versus 0/13, 0%, P = 0.03, linear discriminant analysis, LDA (log 10) and cases culminating in miscarriage (3/6, 50% versus 0/14, 0%, P = 0.017). In the majority of cases (10/14, 71%) bacterial composition was unchanged following cerclage insertion and perioperative interventions. Conclusions Reduced relative abundance of Lactobacillus spp. is associated with premature cervical dilation, whereas high levels of G. vaginalis are associated with unsuccessful rescue cerclage cases. The insertion of a rescue cerclage does not affect the underlying bacterial composition in the majority of cases.