Prolonged labour can occur for several reasons. The muscles of the uterus may not produce sufficiently strong contractions, or may not contract regularly. Some women have uncoordinated contractions, which cause different parts of the uterine muscle to contract at different times. This can result in significant discomfort but minimal progress in labour. Injections may help the contractions, but sometimes a Caesarean section is necessary.
There may also be an obstruction to the passage of the baby through the birth canal (dystocia). This can be caused by the baby having a large head, having the head twisted in an awkward position, or having an abnormal part of the baby presenting (eg. shoulder or face instead of head); or the mother may have a narrow pelvis that does not allow sufficient room for the baby to pass. Sometimes forceps can be used to assist these situations, but often a Caesarean section is necessary for the wellbeing of the baby.
In some women, the cervix fails to dilate and remains as a thick fibrous ring that resists any progress of the baby down the birth canal. In an emergency the cervix may be cut, but in most cases doctors would again prefer to perform a Caesarean section.