Pelvic Floor Anatomy and Parity Influence Risk of Bothersome Vaginal Flatus in First Postpartum Year: Study
Vaginal flatus is a distressing pelvic floor symptom that has received limited research attention, and its prevalence remains unclear. The symptom may be underreported, as women rarely report it without being asked directly. It is defined as the involuntary passage of air from the vagina and is also referred to as “vaginal wind” or a “noisy vagina” in literature. The symptom is commonly provoked by physical activity, postural changes, or exercise. However, sexual intercourse is the most frequently reported trigger. The level of distress caused by vaginal flatus depends on its frequency and the context in which it occurs. Due to its embarrassing nature, vaginal flatus can lead to social discomfort and negatively impact women's quality of life,
The mechanisms underlying vaginal flatus are not fully understood. However, injuries to the pelvic floor, or differences in pelvic floor anatomy, have been suggested as risk factors. One proposed factor is injury to the levator ani muscle at its insertion into the pubic bone, known as levator avulsion. This type of injury is associated with a larger levator hiatus and the sensation of vaginal laxity. In addition, a larger vaginal opening, sometimes referred to as a “gaping vagina”, and a short perineal body have been suggested as contributing factors. Its assessment may be challenging. Although the external measurement of the perineal body with a ruler is widely used, it may overestimate the true size of the perineal body due to overlying skin and subcutaneous fat. Ultrasound may offer an approach that more directly visualizes the perineal body structure.
The limited evidence on vaginal flatus primarily includes participants seeking gynaecological care, which contributes to the relatively high mean age of study populations. Little is known about risk factors for vaginal flatus in younger, childbearing women, or the potential impact of increasing parity. Therefore, the primary objective was to assess the prevalence of and trend in bothersome vaginal flatus from mid-pregnancy to 12 months postpartum, according to vaginal parity. The secondary objective was to assess differences in pelvic floor anatomy as risk factors for bothersome flatus at 12 months postpartum.
Data was collected from the “Perineum study”, a single-centre prospective cohort study at Akershus University Hospital in Norway. Participants completed questionnaires in mid-pregnancy, at 3 and 12months postpartum, and attended a gynaecological examination including ultrasound at 12months postpartum. Parity was classified as primipara, secundipara, or multipara (no, one, or ≥2 previous vaginal births, respectively). A generalised linear mixed model and logistic regression models were used for analysis.
The prevalence of bothersome flatus in mid-pregnancy, at 3 and 12 months postpartum was: primiparas: 0.7%, 4.0%, and 2.5%; secundiparas: 2.3%, 4.4%, and 7.3%; multiparas: 5.4%, 3.0%, and 7.1%, respectively. Compared to primiparas, multiparas had higher odds in pregnancy (OR 14.0, 95% CI 1.8–108.1), and both secundi- and multiparas had higher odds at 12months postpartum (OR 4.8, 95% CI 1.3–17.6, and OR 6.4, 95% CI 1.1–38.6, respectively). Independent risk factors for bothersome flatus included levator avulsion (aOR 3.6, 95% CI 1.5–8.7), a larger genital hiatus (aOR 2.0, 95% CI 1.2–3.3), and a shorter perineal body (aOR 0.8, 95% CI 0.6–1.0).
In this study, authors found that the overall prevalence of bothersome vaginal flatus in pregnancy, at 3 and 12 months postpartum, was low. The lowest prevalence was found among primiparas during pregnancy (0.7%) and highest among secundiparas at 12 months postpartum (7.3%). Increasing parity was associated with more bothersome flatus. However, primiparas experienced a greater increase in symptoms between pregnancy and 3 months postpartum compared to multiparas. Furthermore, results indicate that having a levator avulsion, a larger genital hiatus, and a shorter perineal body height at 12 months postpartum increases the odds of experiencing bothersome flatus.
This study provides valuable insights into the prevalence and trend of bothersome vaginal flatus—a pelvic floor symptom that has received limited research attention. The prevalence of bothersome flatus in a childbearing population is lower than previously described in other populations and is more common in women with previous vaginal births. Levator ani avulsion, a larger genital hiatus, and a shorter perineal body height are independent risk factors for bothersome vaginal flatus. Given the limited body of evidence on vaginal flatus, further research is warranted to explore its impact on quality of life and sexual health, and to address the current lack of research on effective treatment strategies.
Source: Marthe Dalevoll Macedo, Hanne Sether Lilleberg, Jeanette Risløkken;
BJOG: An International Journal of Obstetrics & Gynaecology, 2025; 0:1–8
https://doi.org/10.1111/1471-0528.70063
