Dystocia is an abnormal or difficult labour and/or birth, and affects one per cent of vaginal deliveries. The condition has two categories - cervical dystocia and shoulder dystocia.
Cervical (or uterine) dystocia happens when the woman's cervix fails to dilate sufficiently during labour, meaning that her contractions will not be strong enough to deliver her baby.
Cervical dystocia is classed as a medical emergency. Once diagnosed, doctors will attempt to stimulate contractions with oxytocin and, if this fails, the baby will need to be delivered by caesarean section.
Risk factors for developing cervical dystocia include previous injury to the cervix, maternal obesity and diabetes.
Shoulder dystocia is an extreme medical emergency, and is a rare occurrence affecting 0.6 per cent of births.
It happens when the baby's head has been delivered but the shoulders are stuck at the pelvic brim. This means the baby can inhale, but the chest cannot expand as it is lodged within the woman's pelvis.
Urgent action is required. Failure to do so can result in injury to both the woman and the baby and, in extreme cases, foetal death.
The first course is action is to reposition the woman so that her hips are against her abdomen. Both the woman's and the baby's body are then manipulated in order to help the baby out. This is a highly effective procedure and has a 90 per cent success rate.
If this fails, an episiotomy will be performed and a ventouse and/or forceps will be applied to the baby's head, and various other positions will be used to try and free the shoulders. However, an emergency caesarean will need to be performed if none of these procedures result in a swift delivery.
Risk factors for shoulder dystocia include the woman having a particularly small or abnormally shaped pelvic brim.