The rate of caesarians dramatically increased for 15 years. The main indication of caesarian became the iterative caesarian of principle because of a history of caesarian. Any attempt of reduction of the rate of caesarians should thus focus on the indications of iterative principal caesarean. Nevertheless, the main reason usually evoked to justify a reduction of the attempts of low way after caesarian is the concern generated by the risk of uterine break during the trial of labor. Yet, there is no reliable method to predict this risk of uterine break. A way of interesting research consists in estimating the potential profits of the echography of the scar lower segment. Indeed, the echography can be useful to determine the specific risk of uterine break of a patient by measuring the thickness of the lower segment of the womb.