Exploring profile and potential influencers of vaginal microbiome among asymptomatic pregnant Chinese women

Background This study was designed to explore the profile and potential influencers of the vaginal microbiome (VMB) among asymptomatic pregnant Chinese women and its possible association with pregnancy outcomes. Methods A prospective study was conducted among pregnant Chinese women receiving regular prenatal care at a hospital in Shanghai, China from March 2017 to March 2018. Vaginal swabs were obtained from 113 asymptomatic pregnant women in mid-pregnancy and sequenced by the V3–V4 region of 16S rRNA on an Ion S5™ XL platform. Demographic characteristics and major pregnancy outcomes were collected through questionnaires and electronic medical records. Results The predominant vaginal community state types (CSTs) were CST I (45.1%) and CST III (31.9%). Participants were divided into a lactobacilli-dominant group (LD, CST I/II/III/I–III/V, n  = 100, 88.5%) and a less lactobacilli-dominant group (LLD, CST IV-A/B, n  = 13, 11.5%). Women in the LLD group showed an increased alpha diversity [median (interquartile range, IQR): 2.41 (1.67, 2.49) vs. 0.30 (0.17, 0.59), P  < 0.001], which was related to a lower pre-pregnancy body mass index (BMI) ( P = 0.012), and a greater instance of passive smoking ( P = 0.033). The relative abundance of Lactobacillus was correlated positively with the pre-pregnancy BMI ( r = 0.177, P = 0.041), but negatively with passive smoking ( r  =  − 0.204, P = 0.030). Conclusion The vaginal flora of asymptomatic pregnant Chinese women was mostly dominated by Lactobacillus crispatus and L. iners . A lower BMI and greater instance of passive smoking may contribute to a less lactobacilli-dominant VMB. However, a larger sample size is needed.