Could a mediolateral episiotomy prevent obstetric anal sphincter injury?

Risk factors for obstetric anal sphincter injuries and postpartum anal and urinary incontinence: a case–control trial

“…Whether episiotomy is causative of OASIS or not has been a controversy in multiple papers, with some citing it as a cause and others citing episiotomy as protective [20][21][22]. Recent evidence suggests that more lateral episiotomies might be protective and more medial episiotomies might be causative [23][24][25][26].…”

Obstetric anal sphincter injuries: review of anatomical factors and modifiable second stage interventions

“…Whilst some authors have found a reduction in the rate of OASI with epidural analgesia [53][54][55], others have found no difference [12,41]. Roos et al [56] found that epidural analgesia was the only independent factor that predicted OASI.…”

“…Common intervention choices made in the second stage of labour such as the decision to allow spontaneous tears versus performing an episiotomy, the geometric characteristics of the episiotomy performed, and the choice of instrument for operative vaginal deliveries are to an extent modifiable and can be critical factors in the causation of OASIs. For instance, there is growing evidence to suggest that the chance of sustaining an OASI is 40-50 % higher in women who have a spontaneous perineal tear during their first vaginal birth rather than an episiotomy [5,12]. However, there still remains considerable morbidity due to episiotomies that are either too acute (≤30°) [13,14] or too lateral (≥60°) [15], or originate too close to the midline [15].…”

Primary surgical repair of anterior vaginal prolapse: a randomised trial comparing anatomical and functional outcome between anterior colporrhaphy and trocar‐guided transobturator anterior mesh

“…Unfortunately, no specific data were presented from their hospital to support their claim. The most recent meta-analysis of eight randomised controlled trials, 3 published in 2009, concluded that restrictive episiotomy leads to less severe perineal laceration when compared with routine episiotomy. Hence, we believe that caution should be exercised when ascribing causality between high rates of…”

“…2 Primigravidas had a high incidence of third-and fourth-degree tears when compared with multigravidas (58.8% versus 41.1%), as reported in the paper by Hirayama et al Similar findings have been quoted by other authors. 3 In our hospital, right mediolateral episiotomy is frequently used, as seen in 43.2% (n = 3884) of women. This we believe protects against third-and fourth-degree perineal tears.…”