Reply: Search for a predictive relationship between ultrasound thickness of the lower uterine segment and rupture of the uterus in women with a prior cesarean does not make biological sense

We read with great interest the recent article titled “Evaluation of the usefulness of ultrasound measurement of the lower uterine segment before delivery of women with a prior cesarean: a randomized trial.”1 The authors conclude that “ultrasound measurements of the lower uterine segment (LUS) thickness did not result in a statistically significant lower frequency of maternal and perinatal adverse outcomes than standard management.” Although this conclusion is true, other studies have concluded that “LUS thickness measured by ultrasound during the third trimester of pregnancy is inversely correlated with uterine scar rupture/dehiscence at delivery”2; a conclusion arrived at without demonstrating the practical utility of the method, which has too many false-positives, and above all, false-negative results. However, we completely disagree with the final advice of this study.1 In fact, the authors recommended that “because this study was underpowered, further research should be encouraged.” We are aware that knowing about the risk of uterine rupture causes anxiety to the physicians about the potential adverse outcomes that could be a challenge to manage.3 Nevertheless, we believe that further studies on the subject are totally useless, as after a cesarean delivery, the muscle tissue of the LUS is partially replaced by fibrous tissue4 and not only by muscle tissue. It is known that the strength of muscle tissue is proportional to its thickness; this is not necessarily true of fibrous tissue, which can break despite its thickness. For this reason, we believe that studies relating the thickness of the LUS with any kind of rupture of the uterus have no biological, and consequently, no clinical sense