Abnormal vaginal flora and spontaneous preterm birth in high-risk singleton pregnancies with cervical cerclage

To investigate abnormal vaginal and suture-based bacterial flora for associations with spontaneous preterm birth in high-risk singleton pregnancies with an ultrasound-indicated or emergency cervical cerclage.

A retrospective study of 196 singleton pregnancies with an ultrasound-indicated or emergency cerclage at the Royal Women's Hospital, Australia, from 2004 to 2018. High vaginal swabs were collected regularly between 14 and 26 weeks' gestation, including pre- and post-cerclage insertion, and sent for microscopy and culture. Cervical suture was cultured upon removal. Primary outcomes were spontaneous preterm birth <37, <34 and <30 weeks.

43.4% (85/196) of women delivered preterm. The acquisition and persistence of vaginal Escherichia coli following cerclage insertion were independently associated with spontaneous preterm birth <37 weeks (p = .0225, p = .0477). Escherichia coli growth from the cervical suture upon removal was associated with spontaneous preterm birth <34 weeks (p = .0458). The acquisition of vaginal mixed anaerobes post-cerclage was independently associated with spontaneous preterm birth <34 weeks (p = .0480).

For singleton pregnancies with an ultrasound-indicated or emergency cerclage, the presence of vaginal or suture-based Escherichia coli following cerclage insertion yields increased risk of cerclage failure and spontaneous preterm birth.