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Background

Definition

Vaginal cephalic delivery – that requires additional obstetric manoeuvres to deliver the fetus after the head has delivered.

Objective diagnosis – Prolongation of head – to – body delivery time of more than 60 seconds.

More common – anterior shoulder than posterior.

Implications –

  • Significant perinatal morbidity and mortality.
  • Maternal morbidity – increased incidence of postpartum haemorrhage and third and fourth degree perineal tears.
  • Brachial plexus injury.

 

Brachial Plexus Injury

Brachial plexus injury – one of the most important fetal complications of shoulder dystocia.

Most cases of BPI resolve without permanent disability.

Larger infantsmore likely to suffer a permanent BPI after shoulder dystocia.

Neonatal BPI is the most common cause for litigation related to shoulder dystocia and the third most litigated obstetric-related complication in the UK (as per report published in 2003).

Not all injuries are due to excess traction by healthcare professionals, maternal propulsive force may be contribute to some of these injuries.

Legal point – Important to determine whether the affected shoulder was anterior or posterior at the time of delivery, because damage to the plexus of the posterior shoulder is considered unlikely to be due to the action by the healthcare professional.

 

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Factors associated with shoulder dystocia (Ref : GTG No. 42)

Pre labour Intrapartum
Previous shoulder dystocia
Prolonged first stage of labour
Macrosomia > 4.5 kg
Secondary arrest
Diabetes Mellitus
Prolonged second stage of labour

Maternal BMI > 30 kg/m².

Oxytocin augmentation
Induction of labour
Assisted vaginal delivery

Prevention of Shoulder Dystocia

Induction of labour – NOT prevent shoulder dystocia in non – diabetic women with a suspected macrosomic fetus.

Induction of labour at term – Can reduce the incidence of shoulder dystocia in women with gestational diabetes.

NICE Guideline on Diabetes (NICE : Diabetes, 2008) recommends – Pregnant women with diabetes who have a normally grown fetus should be offered elective birth through induction of labour, or be elective caesarean section if indicated, after 38 completed weeks.

Elective caesarean section – considered in women with diabetes (pre- existing or gestational), regardless of treatment with an estimated fetal weight of greater than 4.5 kg.

Infants of diabetic mothers – 2 – 4 fold increased risk of shoulder dystocia compared with infants of the same birth weight born to non – diabetic mothers.

Ultrasound – To estimate fetal size for suspected large – for – gestational – age unborn babies should NOT be undertaken in a low – risk population.

Prophylactic McRoberts’ positioning before delivery of the fetal head – NOT recommended to prevent shoulder dystocia.

Recommendations for future pregnancy

In women with previous episode of shoulder dystocia :-

Either caesarean section or vaginal delivery can be appropriate.  Decision – jointly by the woman and her carers.

No requirement to recommend elective caesarean birth routinely, but factors such as severity of previous neonatal or maternal injury, if any, predicted fetal size and maternal choice should be considered.

Rate of shoulder dystocia – in women with previous shoulder dystocia10 times higher than in general population.

Recurrence rate  of shoulder dystocia – between 1% and 25%.

Diagnosis of shoulder dystocia

Routine traction in an axial direction can be used to diagnose shoulder dystocia but any other traction should be avoided.

Lateral and downward traction and rapidly applied traction are more likely to cause nerve avulsion.

Management of Shoulder Dystocia

Summon for help.

Fundal pressure – NOT to be used.  Maternal pushing – discouraged.

(Fundal pressure – high neonatal complication rate and may result in uterine rupture). 

McRobert’s manoeuvre – Performed first.  (Success rate – 90%).

McRobert’s manoeuvre – Flexion and abduction of the maternal hips, positioning the maternal thighs on her abdomen.  It straightens the lumbosacral angle, rotates the maternal pelvis towards the mother’s head.

Suprapubic pressure – used to improve effectiveness of the McRobert’s manoeuvre.

Episiotomy – NOT always necessary.  It does not relieve the bony obstruction, but allows more space for internal vaginal manoeuvres.  Use of episiotomy does NOT decrease the risk of Brachial Plexus Injury with shoulder dystocia.

Positioning the woman – Laid flat and any pillows removed from under the back.  If in lithotomy position, her legs will need to be removed from the supports.

Routine axial traction – assess whether the shoulders have been released.

If the anterior shoulder is not released with the McRoberts’ position (± suprapubic pressure) and routine axial traction, another manoeuvre should be attempted.  No clear difference between continuous pressure and ‘rocking movement’.

Internal manoeuvres or ‘all fours’ position  (if McRoberts’ manoeuvre and suprapubic pressure fail).

  • If mother is large – favour delivery of the posterior arm.
  • If mother is slim, mobile woman without epidural anaesthesia with a single midwifery attendant – ‘all fours’ position – more appropriate.

Delivery of posterior arm is associated with humeral fractures with a reported incidence between 2% and 12%.

⇓ (if the above fail)

Third line manoeuvres :-

  • Vaginal replacement of the head (Zavanelli manoeuvre) thendelivery by caesarean section – Most appropriate for the rare bilateral shoulder dystocia.
  • Symphysiotomy – high incidence of serious maternal morbidity and poor neonatal outcome.

Maternal and Neonatal Morbidity in Shoulder Dystocia

Maternal morbidity – 

    • Postpartum haemorrhage (11% cases)
    • Perineal tears (3rd and 4th degree) – (3.8% cases)
    • Others – vaginal lacerations, cervical tears, bladder rupture, uterine rupture, symphyseal separation, sacroiliac joint dislocation and lateral femoral cutaneous neuropathy.

Neonatal morbidity

    • Brachial plexus injury (2.3% – 16% cases).
    • Others – fractures – clavicle and humerus, pneumothoraces and hypoxic brain damage.

Training recommendations

All maternity staff should participate in shoulder dystocia training atleast annually.

Manoeuvres should be demonstrated in direct view.

Higher fidelity training equipment should be used.

Practical training using mannequins – associated with improvements in management.

Training on a high fidelity mannequin – more successful than training with lower fidelity rag doll and pelvis

– higher successful delivery rate ,

– shorter head – to – body interval and 

– lower total applied force successful delivery rate.

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Further Reading

Green Top Guideline No. 42 – Shoulder Dystocia

NICE Guideline – Diabetes

Revise Numbers and Percentages in this article.

Risk factors predicted only 16% of shoulder dystocia that resulted in infant morbidity.

48% of births complicated by shoulder dystocia occur with infants who weigh less than 4000g.

Infants of diabetic mothers – 2 – 4 fold increased risk of shoulder dystocia compared with infants of the same birth weight born to non – diabetic mothers.

Rate of shoulder dystocia – in women with previous shoulder dystocia10 times higher than in general population.

Recurrence rate  of shoulder dystocia – between 1% and 25%.

Delivery of posterior arm is associated with humeral fractures with a reported incidence between 2% and 12%.

Success rate of McRobert’s maneouvre is 90%.

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