Labor is monitored to avoid per partum asphyxia and its consequences. Cardiotocography enables asphyxia detection but carries unuseful cesarean sections. When cardiotocography is not reassuring, fetal pulse oxymetry makes it possible to reduce cesarean section rate for non-reassuring fetal status. Nevertheless, there is an increased number of cesarean sections for dystocia that could be due to the presence of the oxygen sensor itself. A global reduction is mainly observed when oxymetry is associated with fetal blood sampling for pH measurement. In this case, oxymetry also makes it possible to reduce the number of necessary samplings.