Risk of obstetric anal sphincter injury among women who birth vaginally after a prior caesarean section: A state-wide cohort study

The prevention of perineal trauma during vaginal birth

Perineal trauma after vaginal birth is common, with approximately 9 of 10 women being affected. Second-degree perineal tears are twice as likely to occur in primiparous births, with a incidence of 40%. The incidence of obstetrical anal sphincter injury is approximately 3%, with a significantly higher rate in primiparous than in multiparous women (6% vs 2%). Obstetrical anal sphincter injury is a significant risk factor for the development of anal incontinence, with approximately 10% of women developing symptoms within a year following vaginal birth. Obstetrical anal sphincter injuries have significant medicolegal implications and contribute greatly to healthcare costs. For example, in 2013 and 2014, the economic burden of obstetrical anal sphincter injuries in the United Kingdom ranged between £3.7 million (with assisted vaginal birth) and £9.8 million (with spontaneous vaginal birth). In the United States, complications associated with trauma to the perineum incurred costs of approximately $83 million between 2007 and 2011. It is therefore crucial to focus on improvements in clinical care to reduce this risk and minimize the development of perineal trauma, particularly obstetrical anal sphincter injuries. Identification of risk factors allows modification of obstetrical practice with the aim of reducing the rate of perineal trauma and its attendant associated morbidity. Risk factors associated with second-degree perineal trauma include increased fetal birthweight, operative vaginal birth, prolonged second stage of labor, maternal birth position, and advanced maternal age. With obstetrical anal sphincter injury, risk factors include induction of labor, augmentation of labor, epidural, increased fetal birthweight, fetal malposition (occiput posterior), midline episiotomy, operative vaginal birth, Asian ethnicity, and primiparity. Obstetrical practice can be modified both antenatally and intrapartum. The evidence suggests that in the antenatal period, perineal massage can be commenced in the third trimester of pregnancy to increase muscle elasticity and allow stretching of the perineum during birth, thereby reducing the risk of tearing or need for episiotomy. With regard to the intrapartum period, there is a growing body of evidence from the United Kingdom, Norway, and Denmark suggesting that the implementation of quality improvement initiatives including the training of clinicians in manual perineal protection and mediolateral episiotomy can reduce the incidence of obstetrical anal sphincter injury. With episiotomy, the International Federation of Gynecology and Obstetrics recommends restrictive rather than routine use of episiotomy. This is particularly the case with unassisted vaginal births. However, there is a role for episiotomy, specifically mediolateral or lateral, with assisted vaginal births. This is specifically the case with nulliparous vacuum and forceps births, given that the use of mediolateral or lateral episiotomy has been shown to significantly reduce the incidence of obstetrical anal sphincter injury in these groups by 43% and 68%, respectively. However, the complications associated with episiotomy including perineal pain, dyspareunia, and sexual dysfunction should be acknowledged. Despite considerable research, interventions for reducing the risk of perineal trauma remain a subject of controversy. In this review article, we present the available data on the prevention of perineal trauma by describing the risk factors associated with perineal trauma and interventions that can be implemented to prevent perineal trauma, in particular obstetrical anal sphincter injury.

Spontaneous Perineal Trauma during Non-Operative Childbirth—Retrospective Analysis of Perineal Laceration Risk Factors

Childbirth-related perineal trauma (CRPT) is defined as damage to the skin, muscles of the perineum, as well as to the anal sphincter complex and anal epithelium. The aim of the study was to analyze the risk factors for spontaneous injuries to the soft tissues of the birth canal during non-operative delivery. This was a single-center retrospective case-control study. The study included the analysis of two groups, the study group featured 7238 patients with spontaneous perineal laceration (any degree of perineal laceration) and the control group featured patients without perineal laceration with 7879 cases. The analysis of single-factor logistic regression showed that the factors related to perineal laceration during childbirth are the age of the patients giving birth (p = 0.000), the BMI before delivery (p = 0.000), the number of pregnancies (p = 0.000) and deliveries (p = 0.000), diagnosed gestational diabetes (p = 0.046), home birth (p = 0.000), vaginal birth after cesarean (VBAC) (p = 0.001), the use of oxytocin in the second stage of childbirth (p = 0.041), the duration of the second stage of childbirth (p = 0.000), body weight (p = 0.000), and the circumference of the newborn head (p = 0.000). Independent factors that increase the risk of perineal laceration during childbirth are an older age of the woman giving birth, a history of cesarean section, a higher birth weight of the newborn, and factors that reduce the risk of spontaneous perineal trauma are a higher number of deliveries and home birth.