Vaginal Microbiota Characteristics of Pregnancy of Unknown Location Women in China(VMCPULW): Study Protocol for a Prospective Cohort

Abstract Background: Pregnancy of unknown location (PUL) is a kind of pregnancy that has a positive beta-human chorionic gonadotropin (β-hCG) test result but the location of pregnancy cannot be determined by ultrasound. Early determination of the location of the pregnancy is important for subsequent treatment. However, there is no study on the characteristics of vaginal microbiota in pregnant women with unknown locations and a model for judging it by vaginal microbiota combined with clinical indicators. Therefore, we designed this study to compare the characteristics of vaginal microbiota in intrauterine and ectopic pregnancy populations during pregnancy with unknown locations and to establish a prediction model for pregnancy locations in PUL populations with clinical indicators. Methods: This is a prospective, multicenter cohort study. 576 eligible participants will be included in this study. Vaginal microbiota was collected from all participants at inclusion, and color Doppler ultrasound was performed weekly. After the locations of pregnancy were determined, participants of intrauterine pregnancy were followed up to their early pregnancy outcome, and participants of ectopic pregnancy were followed up until a none-pregnancy level of β-hCG was confirmed. Discussion: The regular method of judging the location of pregnancy is by color Doppler ultrasound and β-hCG test. We hope to provide earlier clinical methods of prediction for women with unknown locations of pregnancy through this study.Trial registration: Chinese Clinical Trial Registry: ChiCTR2000035378, registration date: 9 August 2020. http://www.chictr.org.cn/index.aspx