Episiotomy characteristics and risks for obstetric anal sphincter injuries: a case control study
Sir, We read the article by Stedenfeldt et al. evaluating the geometrical properties of episiotomy and the risk of obstetric anal sphincter injury (OASIS) with interest. We would like to compliment the authors for their work, which addresses an important clinical question that has a significant impact on women globally. However, we would like to discuss some points with a view to clarifying the message intended. Firstly, Stedenfeldt et al. compared their result, of an association between a scar episiotomy angle <15 and OASIS, with that of Andrews et al. who found an association between a suture angle of 26 and OASIS. In justifying this comparison, the authors refer to the study by Kalis et al. suggesting a 12 episiotomy angle shrinkage at 6 months after delivery. However, this is potentially misleading because Kalis et al. reported a mean angle shrinkage of 12 when comparing incision and scar angles, and not suture and scar angles. Furthermore, the authors extrapolate evidence from studies investigating the angle shrinkage of mediolateral episiotomies, and use it to support their findings concerning healed lateral episiotomy. In our opinion, the validity of this argument is moot because it does not take into account the effect that the site of incision and the repair technique might have on tissue healing. Secondly, the authors reported no difference between the mean episiotomy angles of their cases and controls. However, they identified a statistically significant association between OASIS and the episiotomy length (e) depth (b) and distance of the starting point of incision to the posterior fourchette (d) In clinical practice, e, angle of incision (a) d and its timing are the only primary independent characteristics considered by the accoucheur. In contrast, b is a secondary variable determined by the other parameters, as stated by the authors in the discussion. Therefore, in our opinion, presenting the additional variable b for consideration by the operator is of limited clinical value. Interestingly, the impact of the primary independent parameters on b can offer a plausible explanation for the difference in the risk association between the angle of incision and OASIS in lateral, compared with mediolateral, episiotomy. In a lateral episiotomy, increasing a, d and/or e could increase b. However, in mediolateral episiotomy (where d 0) b is only determined by a and e. Hence, changes to a affect b more markedly in mediolateral episiotomy. Finally, we recognise that one major limitation for the authors in discussing their findings is that all other studies addressing episiotomy characteristics and risk of OASIS investigated mediolateral episiotomy. We believe both types of incisions have inherent critical differences in the type of structures cut, the mechanism of unloading the perineum and in the repair technique; hence, data from episiotomyrelated studies should be interpreted in the context of the type of episiotomy performed. j
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