Prevalence of Perineal Lacerations in Women Giving Birth at Midwife-Led Birth Centers in Japan: A Retrospective Descriptive Study

Introduction: Perineal lacerations during birth can cause ongoing physical, psychological, and social problems. However, the prevalence of lacerations following normal spontaneous vaginal birth in women with low-risk pregnancies is unknown. We investigated the prevalence of perineal lacerations and factors associated with lacerations among low-risk Japanese women who had normal spontaneous vaginal births.

Methods: Pregnant women who were cared for between January 1, 2008, and June 30, 2011, in 3 midwife-led birth centers in Tokyo, Japan, where invasive medical interventions are rarely applied, were included. We investigated the prevalence of perineal lacerations and conducted univariate and multivariate analyses on the relationship between the prevalence of lacerations and selected maternal and neonatal characteristics.

Results: A total of 1881 pregnant women had initial antenatal care at one of the 3 study sites. Of these, 1521 were eligible for inclusion. Intact perineum rates were 49.5% (209/422) and 69.9% (768/1099) in nulliparous and multiparous women, respectively. First-degree lacerations occurred in 36.7% (155/422) of nulliparous women and 27.1% (298/1099) of multiparous women, and second-degree lacerations occurred in 13.5% (57/422) of nulliparous women and 3.0% (33/1099) of multiparous women. One multiparous woman experienced a third-degree laceration (0.1%). No women suffered fourth-degree or cervical lacerations. Logistic regression analyses showed that older age (≥ 35 years), the hands-and-knees position, and using a birthing chair during birth increased the risk of perineal laceration both in nulliparous and in multiparous women. In addition, waterbirths increased the risk of perineal laceration in multiparous women.

Discussion: In normal spontaneous vaginal births among a low-risk population, it is possible to avoid episiotomy and achieve a high rate of intact perineum, with few second-degree and third-degree lacerations.