Re: Prevalence, potential risk factors for development and symptoms related to the presence of uterine niches following Cesarean section: systematic review.

Abstract

According to a recent systematic review published in this Journal1, ‘single-layer myometrium closure’ proved to be a risk factor for niches or even large niches, as stated in the abstract, results section and discussion section of this paper. This may suggest to the reader that single-layer closure of the uterine incision should be avoided. In a recent multicenter, case–control study a similar conclusion was, in retrospect, drawn prematurely: women attempting a trial of labor after Cesarean section with single-layer uterine closure carried more than twice the risk of uterine rupture than did those with double-layer closure, and single-layer closure ‘should be avoided in women who could contemplate future vaginal birth after cesarean delivery’2. However, in a subsequent, more detailed meta-analysis on single- vs double-layer closure, including the same data and taking into account the locked vs unlocked modification of the single-layer technique, the findings showed that it was specifically the locked but not the unlocked modification that increased the risk of uterine rupture. Moreover, unlocked single-layer closure showed a trend towards lower risk of rupture compared with that of double-layer closure (odds ratio, 0.49), but this difference did not reach statistical significance3. Thus, it seems that the locked modification of the single-layer suture may increase the risk of uterine rupture, possibly because the surgically better hemostatic effect at the site of the incision margins is at the cost of greater tissue hypoxia and subsequent deficient healing. Women with a niche after Cesarean section may in the next pregnancy be at risk of both uterine rupture, because of decreased myometrial thickness, and placenta accreta, because of the healing defect4, in both cases at the site of the niche. Hence, it could be important to clarify whether it is the single-layer myometrium closure per se that constitutes a risk factor for a niche or whether differentiation should be made between the locked and unlocked single-layer modalities. There are also conflicting results published concerning the double-layer closure technique, there being fewer uterine scar defects when starting with a continuous suture of the decidua as a first layer5, yet there being a higher risk of placenta accreta in subsequent pregnancies when starting with a continuous suture ‘on the inner side of the uterine wall’6. In view of these conflicting reports, I would like to ask the authors whether this aspect of locked vs unlocked modification of the single-layer technique has been considered and if they have found any studies addressing this issue. M. Gonser Clinic of Obstetrics and Prenatal Medicine Ludwig-Erhard-Str. 100, Wiesbaden 65199, Germany (e-mail: m.gonser@gmx.de)