I read with interest the paper by Shek and Dietz,1 and congratulate the authors for an informative study. With all its limitations, such as early postpartum follow-up, the authors have described a new form of birth trauma (irreversible overdistension injury), which is distinct from levator avulsion injury, and cannot be detected by static magnetic resonance imaging (MRI). In their study, 13% of women after a normal vaginal delivery had levator avulsion diagnosed. I would be grateful if the authors could clarify how many of these women had an episiotomy and how many sustained a perineal tear. Similarly, I would be grateful for clarification on how many of the 28.5% of vaginally parous women diagnosed with ‘levator microtrauma’ had normal deliveries, and what proportion had episiotomies and perineal tears.
Levator avulsion (macrotrauma) has also been detected on MRI scans, and is believed to result from avulsion from the origin of the muscle at the pubic symphysis. I would be grateful if the authors could suggest how ‘levator microtrauma’ (which implies patchy infarcts or ischaemia) would lead to a permanent overdistension of the levator hiatus. Instead, one wonders whether disruption of the perineal body (which is the midline union of muscles and endopelvic fascia) is another possible mechanism of irreversible traumatic overdistension of the levator hiatus. Indeed, whereas the levator can distend to 1.5 times its size, fascia would probably have a lower threshold for disruptions. On clinical examination, a widened urogenital hiatus is often correlated with a deficient perineum.
Recent work has shown that mediolateral episiotomies are closer to the midline than was previously believed.2,3 One wonders whether acutely angled episiotomies and midline perineal tears (especially anal sphincter injuries) are contributory factors to perineal body disruption and consequent overdistension injury.
The authors conclude by suggesting modifications in current obstetric practices to prevent levator trauma, without specifying what these are. I would be grateful for their thoughts on whether a well-directed mediolateral episiotomy could reduce the risk of overdistension injury, as has been suggested by DeLancey.4
Also, is the timing of the episiotomy important? Is the damage already done by the practice of giving episiotomies at crowning? Would performing an episiotomy prior to the crowning of the head help in preventing irreversible overdistension injury?