Vulvar Lichen Sclerosus as a Risk Factor for Birth-related Perineal Tear

Vulvar lichen sclerosus is a chronic inflammatory skin disease that predominantly affects the anogenital region. While typically observed in postmenopausal women, it may also occur in women of reproductive age. The condition is diagnosed in approximately 1.7% of women; however, the actual prevalence is likely underestimated due to underdiagnosis and underreporting. Despite well-documented effects on vulvar anatomy and tissue integrity, evidence regarding its impact during pregnancy and childbirth remains limited.

To evaluate whether women diagnosed with vulvar lichen sclerosus have an increased risk of obstetric perineal tears during vaginal delivery compared with unaffected women. A secondary objective was to identify potential risk factors associated with obstetric anal sphincter injuries in women with vulvar lichen sclerosus.

Medical records of women diagnosed with vulvar lichen sclerosus who gave birth in the North Denmark Region between October 1, 2019 and September 30, 2024 were included. For each birth given by a woman with vulvar lichen sclerosus, the next two births occurring in the Region by women without the diagnosis were selected as controls. To investigate for associations with perineal tears, maternal and obstetric factors were described and compared between the two groups, while relative risk was estimated with corresponding confidence intervals (CI). To identify factors associated with obstetric anal sphincter injuries in the vulvar lichen sclerosus group, bivariate regression models were performed based on significant differences between mild perineal tears (not requiring suturing, first- and second-degree tears) and obstetric anal sphincter injury.

In total, 277 medical birth records of women with vulvar lichen sclerosus and 533 controls were included. In multivariable analysis adjusted for parity, birth weight, head circumference, and vacuum-assisted delivery, vulvar lichen sclerosus was associated with a significantly increased risk of second-degree tears (relative risk 1.37, 95% CI 1.14-1.65, p <.001) and obstetric anal sphincter injuries (relative risk 3.37, 95% CI 1.30-8.76, p = 0.01) when compared with controls. In the vulvar lichen sclerosus group, bivariate analysis revealed a significant association between obstetric anal sphincter injuries and nulliparity (relative risk 4.91, 95% CI 1.10-21.91, p = 0.04), vacuum-assisted delivery (relative risk 6.50, 95% CI 2.19-19.28, p <.001), narrowing of the vaginal introitus (relative risk 6.20, 95% CI 1.66-23.17, p = 0.007), symptoms during pregnancy (relative risk 3.98, 95% CI 1.35-11.75, p = 0.01), and duration of the second stage of labor (relative risk 1.01, 95% CI 1.00-1.02, p = 0.02).

Vulvar lichen sclerosus was significantly associated with an increased risk of second-degree tears and obstetric anal sphincter injury after adjustment for obstetric variables. In the vulvar lichen sclerosus group, narrowing of the vaginal introitus and symptoms during pregnancy were associated with an increased risk of obstetric anal sphincter injury.