Causes and consequences of malpresentations and malpositions

In the majority of individual cases it may not be possible to identify what caused the baby to be in an abnormal presentation or position during delivery. However, the general conditions that are thought to increase the risk of malpresentation or malposition are listed below:

• Abnormally increased or decreased amount of amniotic fluid
• A tumour (abnormal tissue growth) in the uterus preventing the spontaneous inversion of the fetus from breech to vertex presentation during late pregnancy
• Abnormal shape of the pelvis
• Laxity (slackness) of muscular layer in the walls of the uterus
• Multiple pregnancy (more than one baby in the uterus)
• Placenta previa (placenta partly or completely covering the cervical opening).

If the baby presents at the dilating cervix in an abnormal presentation or malposition, it will more difficult (and may be impossible) for it to complete the seven cardinal movements. As a result, birth is more difficult and there is an increased risk of complications, including:

• Premature rupture of the fetal membranes (PROM)
• Premature labour
• Slow, erratic, short-lived contractions
• Uncoordinated and extremely painful contractions, with slow or no progress of labour
• Prolonged and obstructed labour, leading to a ruptured uterus
• Postpartum haemorrhage

With these complications in mind, we now turn your attention to the commonest types of malpresentation and how to recognise them.