Shoulder dystocia: what it is and what happens at birth

In shoulder dystocia the baby's head is born, but one shoulder becomes stuck behind the mother's pubic bone, delaying the birth of the body. The RCOG says extra help is usually needed to release the shoulder, and that in the majority of cases the baby will be born promptly and safely. It is treated as an emergency because the baby cannot start breathing air into the lungs until the body is born.

The RCOG says shoulder dystocia usually occurs unexpectedly and most of the time it is not possible to predict. It is more likely in the situations listed below. The leaflet also notes that large babies are more likely to be affected, yet most babies over 4.5 kg are born without difficulty and half of all cases involve babies under 4 kg. Scans are not good at telling whether a baby will be large, so the RCOG does not recommend them to predict shoulder dystocia in the absence of other risk factors.

• You have had shoulder dystocia before.

• You have diabetes, including diabetes that developed in pregnancy.

• Your body mass index is 30 or more.

• Your labour is induced, or is long.

• You have an assisted vaginal birth with forceps or ventouse.

In most cases it cannot be prevented because it cannot be predicted. The RCOG leaflet says that if you have diabetes you will usually be offered early induction or a planned caesarean, which reduces the risk. For women without diabetes the leaflet (published in 2013) says early induction does not prevent shoulder dystocia even if the baby is thought to be large, and caesarean is not routinely recommended.

More recent NICE guidance on inducing labour (NG207) frames suspected large babies in women without diabetes as a choice between waiting, induction or caesarean. NICE says induction reduces the risk of shoulder dystocia compared with waiting but increases the risk of third- or fourth-degree tears, and that the risk of perinatal death, brachial plexus injury or emergency caesarean is the same either way. NICE defines a suspected large baby as an estimated weight above the 95th centile at or after 36 weeks. Because guidance has moved on, ask your team which advice they are following and why. For diabetes in pregnancy, NICE points to its separate diabetes guideline.

Your midwife presses the emergency bell and three or four staff, including obstetricians, midwives and a doctor for the baby, usually come to the room. The RCOG acknowledges this can be frightening for you and your birth partner, but notes that staff are trained in the manoeuvres. The usual first steps are to ask you to stop pushing, to reposition you onto your back with your legs pushed outwards and up towards your chest (the McRoberts manoeuvre), to press on the abdomen just above the pubic bone, and to consider an episiotomy.

If these do not work easily, the obstetrician or midwife may put a hand in the vagina to free the shoulder, or you may be helped onto all fours. After the birth a paediatrician examines the baby and your team talks through what happened.

For you, the RCOG says vaginal tears are more common and may extend to the back passage, and heavier bleeding after birth (postpartum haemorrhage) is more common, sometimes needing extra treatment or a blood transfusion. Tommy's lists shoulder dystocia among the factors that make a more serious tear more likely.

For the baby, the RCOG says about 1 in 10 babies who have shoulder dystocia have some stretching of the nerves in the neck, called brachial plexus injury, which may cause loss of movement in the arm; the most common type is Erb's palsy. It is usually temporary and movement returns within hours or days, and permanent damage is rare. The leaflet stresses that brachial plexus injury can also occur without shoulder dystocia and after caesarean birth. Fractures of the arm or shoulder can occur and usually heal very well. Very rarely, a baby can suffer brain damage if the delivery was delayed by shoulder dystocia and oxygen was short.

The RCOG says there is an increased risk in future pregnancies, with around 1 in 10 women having shoulder dystocia again. Your obstetrician or midwife will discuss options taking account of your circumstances. The leaflet says you may wish to consider a vaginal birth if it was easy to release the shoulders, the baby was fine and you have no other risk factors, and a planned caesarean if release was difficult, the baby was injured or the experience has affected you and your family. If you want to talk about what happened later, the RCOG suggests your obstetrician, midwife, health visitor or GP.