Definition Shoulder dystocia occurs when the baby’s head has been born but a shoulder becomes impacted behind the mother’s pelvic bone, resulting in a delivery that requires additional obstetric manoeuvres to release the impacted shoulder (s) after a gentle downward traction has failed. This is a ‘bone–bone problem’ at the level of the pelvic inlet (Figure 12.1).
Figure 12.1 Demonstration of shoulder dystocia as a ‘bony problem’ at the pelvic inlet.
Incidence Approximately 0.5% (5 of 1000).
Fetal: Peripartum hypoxia resulting in stillbirths; neonatal admission for convulsions and multi-organ support; long-term neurological outcomes (learning difficulties, cerebral palsy); and neonatal injuries such as fractures (clavicle, humerus), brachial plexus injuries (4%–16%) and Erb’s palsy (10%).
Medico-legal: Clinical negligence claims due to delay in delivery, inappropriate or excessive traction to deliver the shoulders.
Key Diagnostic Signs
Various mnemonics have been described to aid remembering the many manoeuvres that have been described to manage shoulder dystocia. However, the choice of a manoeuvre should depend on the specific clinical situation (e.g. ‘all fours’ may be the manoeuvre of first choice in homebirths but not in a hospital setting in a woman having epidural analgesia), skill and experience of the accoucher (e.g. some clinicians may prefer delivery of the posterior arm to rotatory manoeuvres), patient characteristics (e.g. McRoberts manoeuvre may not be appropriate in a woman with a history of hip injury) and fetal condition (e.g. shoulder dystocia in a large macrosomic fetus who has sustained an intrauterine death will not require alerting the neonatal team and cleidotomy may be considered early) [1, 2].
We have classified the manoeuvres into ‘first line’ (SPR) and ‘second line’. The latter should be used when the first-line manoeuvres fail and are associated with increased maternal and fetal morbidity. Therefore, consultant (or experienced) obstetric presence is recommended during the performance of second-line manoeuvres.
Manoeuvres are described in the text that follows, assuming that the fetal back is facing maternal left side. If the fetal back faces maternal right, it is recommended that clinicians use their opposite hand to facilitate these manoeuvres.
First-Line Manoeuvres (SPR)
Shout for help (experienced midwives and obstetricians, neonatologist, anaesthetist) as soon as shoulder dystocia is diagnosed and Specify emergency (‘shoulder dystocia’). If shoulder dystocia has been anticipated based on risk factors, experienced midwives and obstetricians should be on ‘stand-by’ when active pushing commences and when delivery is imminent.
Stop traction and advise the woman to stop pushing.
Scribe – assign someone to keep a contemporaneous record of the time and the action taken and to alert every minute.
Position the buttocks at the edge of the couch to enable manoeuvres that may later become necessary. Position the thighs – flexed at the hip over the maternal abdomen and externally rotated (McRobert’s manoeuvre) by two attendants (Figure 12.2). This will achieve delivery of the shoulders in approximately 90% due to sliding of the sacral promontory upwards. Attempt ‘roll over’ or ‘all fours’ position, which may increase the diameter of the maternal pelvis due to ‘sliding’ of the sacral promontory upwards. This manoeuvre may be attempted first in settings where placing a woman in a McRobert’s manoeuvre may not be immediately feasible (i.e. homebirths) and when the woman does not have an epidural analgesia (i.e. no restriction of movements).
Figure 12.2 McRobert’s manoeuvre: maternal thighs flexed at the hip, abducted and externally rotated by two birth attendants.
Pressure – (supra-pubic pressure) – first in a continuous motion for 30 seconds and later in a ‘rocking motion’ similar to cardiopulmonary resuscitation (CPR) after identifying the fetal back (Figure 12.3). A birth attendant should stand facing the fetal back and attempt to push the anterior shoulder away from the symphysis pubis. This will help the shoulders enter into the maternal pelvic inlet through the larger oblique or transverse diameter.