Unstable Lie , Malpresentations , and Malpositions IAN

The concepts of unstable lie, malpresentation, and malposition have not changed for centuries probably, and there is no reason to anticipate a significant change will present in the foreseeable future. Various techniques for improving diagnostic accuracy and clinical care are periodically proposed and either become established clinical practice or disappear, sometimes to be resurrected at a later date. Near term and during labor, the fetus usually assumes a longitudinal lie and presents to the maternal pelvis with the head, the neck flexed, and the vertex in the lowermost part of the uterus. In approximately 5% of labors, the lie is not longitudinal; this can be dangerous for both mother and fetus and demands intervention. As with much of medicine, the prior identification of the pregnancy at particular risk for unstable lie, malpresentation, or malposition can prompt intervention in advance of a complication developing and improve the outcome. Although relevant to unstable lie and malpresentation, this chapter does not consider issues relating to fetal breech presentation in detail because these are dealt with elsewhere (see Chapter 63).