Shoulder dystocia

Definition

• A distinction is made between high bisacromial and deep transverse arrest; the more dangerous form is the high bisacromial arrest.
• The turtle neck sign describes the retraction of the head against the perineum.

• In shoulder dystocia, after birth of the head the anterior shoulder becomes impacted behind the pubic symphysis, less commonly the posterior shoulder behind the sacral promontory.
• It is characterised by failure of the shoulders to be born with gentle downward traction and the need for additional obstetric manoeuvres; a head-to-shoulder interval of more than 60 seconds has been proposed as an objective criterion.

Occurrence & epidemiology

Figures

• Overall, shoulder dystocia occurs in 0.5–1% of all vaginal births.
• The recurrence risk is at approx. 14%.

Epidemiology

• Shoulder dystocia occurs in about 0.2 to 3% of vaginal births in vertex presentation.
• The incidence rises with birth weight from about 0.3–1% at 2,500 to 4,000 g to 5–7% at 4,000 to 4,500 g; nevertheless, more than half of cases involve infants of normal birth weight.

Aetiopathogenesis

Risk factors

• They include macrosomia, diabetes, obesity, prolonged labour.
• In diabetic women the risk is higher because the trunk grows disproportionately.

Aetiology and risk factors

• The cause is a shoulder (biacromial) diameter that is too large relative to the birth canal.
• Risk factors are fetal macrosomia, maternal obesity, diabetes mellitus, shoulder dystocia in a previous pregnancy, forceps or vacuum birth and very rapid or prolonged labour.
• An early warning sign is a prolonged second stage, particularly in fetuses with risk factors.

Clinical features

More facts from the study questions

• The recurrence risk for shoulder dystocia is stated to be approximately 14 percent.
• In pregnant women with diabetes mellitus, disproportionate growth of the foetal trunk is common.
• This leads to broader shoulders and increases the risk of shoulder dystocia.
• The necessary manoeuvres and the prolonged second stage of labour increase the risk for the mother.
• Typical maternal complications include uterine atony and high-grade perineal or cervical tears.
• Although macrosomia is a significant risk factor, the majority of shoulder dystocias occur unexpectedly.
• Most cases happen in infants with a normal birth weight.
• The aim is to adduct the anterior shoulder and rotate it under the symphysis pubis.
• The Kristeller manoeuvre and traction on the head are strictly contraindicated in shoulder dystocia.
• Both manoeuvres can worsen the shoulder impaction and lead to severe injury of the fetal brachial plexus.

Clinical features and complications

• The born head may retract against the perineum (turtle sign); however, only some cases show this sign.
• Brachial plexus injuries occur in about 7–20% of shoulder dystocias, more often on the right; the most common is upper plexus palsy (Erb, C5–C6), less often lower plexus palsy (Klumpke, C8–T1) or complete palsy; most resolve within 6–12 months, but about 10% of Erb palsies do not.
• Further neonatal consequences are clavicular and humeral fractures and, with prolonged dystocia, fetal compromise up to asphyxia and death.
• Maternal complications are postpartum haemorrhage, perineal tears, anal sphincter injuries, symphysis pubis separation and lateral femoral cutaneous neuropathy.

Diagnosis

• Shoulder dystocia is a clinical diagnosis made only when it occurs: the head has been born but the anterior shoulder does not follow despite gentle traction.
• Fetal weight alone is not a reliable predictor.

Keep learning in the app

Further reading (selection)

1. DocCheck Flexikon, Schulterdystokie

Cross-references