Abstract Study question What are the intimate hygiene practices of women in IVF treatment and do they correlate with the vaginal microbiota? Summary answer Hygiene practices, in specific douching and use of intimate soap significantly increased the risk of abnormal vaginal microbiota (AVM). What is known already The normal vaginal microbiota acts as a defense system against infection. AVM is a molecularly defined vaginal dysbiosis, resembling bacterial vaginosis (BV) and is dominated by anaerobic bacteria such as Gardnerella vaginalis. Importantly, AVM is associated with an increased risk of genital tract infections, poor IVF outcomes, early miscarriage and preterm labor. The cause of AVM is multifactorial and hygiene practices may interrupt the normal microbiota. Previous small studies suggested vaginal douching to be associated with an increased risk of AVM. Few studies have investigated the possible correlation between intimate hygiene practices, menstrual practices and the vaginal microbiota. Study design, size, duration Observational cohort study, including a total of 1421 IVF patients from four Danish fertility centers. The inclusion period was from 2017 to January 2022. Participants/materials, setting, methods Patients aged 18-42 years and undergoing their first, second or third IVF stimulation cycle were eligible for inclusion. The intimate hygiene practices in terms of type of soap, menstrual protection, douching and probiotics, were reported in a structured questionnaire including a total of 40 questions. Vaginal swabs were obtained prior to ovarian stimulation and subsequently subjected to quantitative PCR testing, targeting DNA of dysbiotic bacteria. Main results and the role of chance AVM was present in a total of 34 % (479/1421) of women, and 20% (272/1384) reported vaginal douching, which significantly correlated with AVM (p < 0.01, OR = 1.62 [1.23-2.12]). Intimate soap was used by 39 % (535/1384) of patients, which also significantly increased the risk of AVM ( P = 0.04, OR = 1.35 [1.08-1.69]). Water only was used by 36% (492/1384), and regular soap was used by 27% (374/1384). No correlation between use of water only and regular soap and AVM was detected. For menstrual protection 40% (433/1078) used pads, followed by tampons alone 25% (265/1078) or a combination 21% (230/1078), and 14 % (148/1078) used a menstrual cup. A trend for an increased risk of AVM when using tampons, OR 1.21 [0.91-1.62] was seen whereas use of a menstrual cup seemed to lower the risk of AVM, OR 0.71 [0.48-1.04] Active smoking, higher BMI, drinking >7 units per week and previous chlamydia infection significantly correlated with AVM (p = 0.01, p = 0.01, p = 0.04 and p = 0.01). Finally, 84% (1190/1421) reported gynecological symptoms such as vaginal discharge, dyspareunia and fungal infection, but only fishy odor significantly correlated with AVM (p < 0.01). Limitations, reasons for caution To the best of our knowledge, this is the largest study investigating the intimate hygiene practice and its correlation with AVM in an IVF population. As these results describe the practices of a Scandinavian IVF population, results may differ from other settings and ethnicities. Wider implications of the findings Exploration of the cause-and-effect relations between intimate hygiene practices and AVM is needed, requiring intervention-based prospective studies. This would lead to evidence-based advice on intimate hygiene practices and AVM prevention, possibly increasing live birth rates. The unexpected high prevalence of douching in a Danish IVF population needs further exploration. Trial registration number NCT03420859

The aim of the present randomised, double-blind, placebo-controlled trial was to investigate whether antibiotics and live lactobacilli would improve clinical pregnancy rates in IVF patients with abnormal vaginal microbiota (AVM) defined by high quantitative PCR loads of Fannyhessea vaginae and Gardnerella spp. IVF patients were randomised prior to embryo transfer into three parallel groups 1:1:1. Group one (CLLA) received clindamycin 300 mg ×2 daily for 7 days followed by vaginal Lactobacillus crispatus until the day of pregnancy scan, using the investigational drug LACTIN-V. Group two (CLPL) received clindamycin and placebo LACTIN-V, and finally, group three (PLPL) received an identical placebo of both drugs. A total of 1533 patients were screened, and 338 patients were randomised. The clinical pregnancy rate per embryo transfer was 42% (95%CI 32-52%), 46% (95%CI 36-56%) and 45% (95%CI 35-56%) in the CLLA, CLPL, PLPL groups respectively. Thus, treatment of AVM does not improve reproductive outcome. The EudraCT (European Union Drug Regulating Authorities Clinical Trials Database) clinical trial identifier is 2016-002385-31; first registration day 2016-07-11.