LAUSR

541 The vaginal microbiota differs between women who deliver preterm relative to those who deliver fullterm David A. Crosby, Conor Feehily, Raul Cabrera-Rubio, Shane Higgins, Paul Cotter, Fionnuala McAuliffe National Maternity Hospital, Dublin, Leinster, Ireland, UCD, Perinatal Research Centre, University College Dublin, Dublin, Leinster, Ireland, Teagasc, Moorepark Food Research Centre, Fermoy, Cork, Munster, Ireland, APC Microbiome Institute, University College Cork, Cork, Munster, Ireland OBJECTIVE: Perturbations in the vaginal microbiota, and more specifically bacterial vaginosis (BV), have been linked to preterm birth (PTB). Indeed, there is a reported 2-fold increase of preterm birth in women diagnosed with BV during pregnancy. BV is characterised by a shift in healthy populations of lactobacilliin the vagina towards a more mixed-species microbiota that mainly includes Gardnerella vaginalis, Atopobium vaginae and Prevotella sp., among others. Despite the reported link between BVand PTB, controversy remains. Our study aimed to use next generation sequencing techniques to examine the relationship between the vaginal microbiota and preterm birth. STUDY DESIGN: 37 pregnant women after 10 weeks gestation who were at risk of pre-term delivery and a further 11 pregnant women deemed not at risk were recruited and the associated vaginal microbial composition (16S rRNA) determined. Patient demographics are illustrated in table 1. RESULTS: It was established that distinctly different patterns of Lactobacillus populations were evident within samples collected from the 8 women who subsequently delivered preterm compared to those who had full-term pregnancies (Figure 1). Notably, L. crispatus was significantly reduced in the preterm birth group. It was also evident that the preterm birth group clustered into two distinct community state types, CST-V & CST IIIa, dominated by L. jensenii and L. iners, respectively. There was no significant difference in microbial diversity across groups nor was a distinct BV associated community identified in the preterm group. CONCLUSION: Overall this study provides an important further insight into the vaginal microbiota of PTB. The repeated finding that L. crispatus is a dominant group in the FTB vaginal microbiome is, potentially of great importance in the context of the possible modulation of the vaginal microbiota to reduce the risk of PTB.