Effects of the sampling time on the vaginal microbiota in healthy pregnant women: a prospective observational study.

Background: Studies using 16S rRNA gene sequencing have extensively examined the vaginal microbiota changes of pregnant women. However, no study has examined these changes considering the time of day at which vaginal fluid samples were collected from near-term pregnant women. Objective: To describe the vaginal microbiota of Japanese near-term pregnant women with normal pregnancy outcomes and potential vaginal microbiota changes from wake-up to bedtime. Study design: In this prospective observational study, vaginal swab specimens were obtained from healthy near-term pregnant women twice on the same day, after waking up and before bedtime. All specimens were examined for total bacterial cell count per gram of vaginal fluid, Nugent score, pH, and vaginal microbiota analysis using 16S rRNA gene sequencing. Initially, the wake-up and bedtime samples of all participants were analyzed at the genus level using next-generation sequencing. Subsequently, all samples were analyzed at the genus and species levels using Sanger sequencing. Results: Sixteen pregnant women were enrolled in this study. The median age of the participants was 32.5 years, and the median gestational age was 38 weeks. Median bacterial counts in vaginal fluids at wake-up and bedtime were 3.9 × 10 Conclusions: The vaginal microbiota of pregnant women with normal pregnancy outcomes was not necessarily dominated by