Cephalopelvic disproportion: this woman's pelvis is too small for her baby's head.
Persistent malpresentation or malposition are other major causes of obstructed labour.
Can you distinguish between these two terms and recall some abnormal fetal presentations and malpositions?
Show answer
Malpresentation is any presentation other than vertex (the top of the baby's skull is the presenting part). The most common malpresentations are breech (the baby's buttocks and/or its feet present first), and shoulder when it engages 'shoulder first'. Malposition is when the baby is 'head down' (cephalic presentation), but the vertex is in the wrong position relative to the mother's pelvis. Two of the most common malpositions result in face and brow presentations.
Labour can be obstructed by locked twins (the two babies are 'locked' together at their necks when the first twin is in breech presentation and the second twin is in cephalic presentation), or conjoined twins (twins fused at the chest, head or any other site).