Reducing perineal trauma: implications of flexion and extension of the fetal head during birth.

In this paper a critical analysis of two popular perineal management techniques used during birth, flexing the baby's head and the Ritgen manoeuvre, are presented. Each technique claims to reduce perineal trauma by reducing the presenting diameter of the fetal skull through the woman's vaginal opening. These two techniques are, however, contradictory and act against the normal mechanisms of labour. In normal labour, the smallest diameter of the fetal skull, the suboccipito-bregmatic, presents through the woman's vaginal opening. In order to negotiate the 90 degrees curve in the birth canal, the baby must change from an attitude of flexion to an attitude of extension during birth. The Ritgen manoeuvre encourages early extension of the fetal head which causes a larger fetal head diameter, the occipito-frontal diameter, to present. Flexing the fetal head cannot cause a smaller diameter to present, and the pressure the birth attendant applies to flex the head serves only to retard the emergence of the baby and unnaturally force the emerging fetal head down toward the stretched perineum. The discussion outlines the implications of this analysis for practice.