A new review published in npj Women’s Health examines the current understanding of vaginal biomechanics and its role in menstruation, sexual intercourse, pregnancy, and childbirth. The comprehensive study analyzes decades of research, highlighting how limited and inconsistent data have affected progress in women’s health innovation.
The review found that despite the vagina’s ability to stretch from a 2.5 cm diameter to 10 cm during childbirth, researchers still lack adequate understanding of its mechanical properties. Nearly 80% of vaginal deliveries result in some tissue trauma, and 30% of women who have undergone vaginal delivery develop at least one pelvic floor disorder – three times higher than in women who have never been pregnant.
Current research methods show significant limitations in capturing tissue mechanics. While uniaxial tensile testing has been the most popular method, it fails to replicate the multi-directional forces that vaginal tissue experiences in vivo. Most studies have focused on testing in the longitudinal direction alone, neglecting crucial circumferential forces experienced during childbirth and other functions.
The review identifies several critical gaps in current knowledge. Only a limited number of studies have investigated the tissue’s viscoelasticity – its time-dependent mechanical properties. This gap is particularly significant for understanding childbirth mechanics, as the second stage of labor can have an extended duration where these properties become crucial.
Another key finding concerns tissue hydration during testing. The researchers note that many studies have not maintained proper tissue hydration during experiments, potentially affecting results. The vagina is naturally hydrated by continuous fluid supply, and exposure to atmospheric conditions can alter its mechanical properties.
Animal studies, while valuable for controlled experiments, have shown limitations in translating findings to humans. For instance, the effects of pregnancy on vaginal tissue appear consistent across animal models, showing increased compliance and distensibility. However, the long-term effects of childbirth differ significantly between species, complicating the development of treatments for human conditions.
The impact of menopause on vaginal biomechanics remains unclear. While menopause is generally believed to increase tissue stiffness in humans, most studies haven’t properly controlled for age – a factor independently associated with increased tissue stiffness. Animal models using ovariectomy to simulate menopause have shown conflicting results.
The review also examines the relationship between vaginal biomechanics and pelvic organ prolapse. Interestingly, ex vivo and in vivo testing methods have yielded opposing results. While most ex vivo studies show increased tissue stiffness with prolapse, in vivo testing indicates tissue softening. This discrepancy might result from the tissue being tested in isolation versus its natural state connected to surrounding pelvic organs.
The authors emphasize the need for standardized testing methods and increased collaboration between biomechanics experts and gynecologists. They suggest that new experimental techniques should be developed to better simulate physiological conditions and measure properties in multiple anatomical directions simultaneously.
Looking ahead, the review points to promising developments in computational modeling. These models could help explore scenarios that can’t be studied experimentally due to ethical considerations or technical limitations. As more data becomes available through improved testing methods, machine learning approaches could help fill knowledge gaps and advance treatment strategies.
The authors conclude that this understudied field requires sustained research efforts to develop new diagnostic tools and treatments that could significantly improve women’s quality of life throughout various life stages. The findings have particular relevance for the development of new medical devices, surgical techniques, and therapeutic approaches in women’s health.
