What is shoulder dystocia?
It’s an obstetric emergency in cephalic vaginal delivery where gentle traction fails to deliver the shoulders after head has been delivered, requiring additional obstetric maneuvers.
More objectively it can be diagnosed when shoulders are not delivered, 60 seconds after the head delivery.
This will complicate 1% of all deliveries.
Why does it occur?
It’s commonly due to bony impaction of anterior shoulder against pubic bone, or rarely posterior shoulder against sacral promontary.
Why it is an emergency?
It carries mobidity and mortality for both mother and fetus. And it occurs in unpredictable pregnancies most of the time.
Mother- PPH-11%
Soft tissue injuries- 3rd &4th degree tears-4%
Fetus- Hypoxia ( causing acidosis with ischeamic encephalopathy)
Brachial plexus injury
Clavicular and humerus fractures
What is the prevalence of brachial plexus injury?
BPI will complicate 4-16% of all SD.
Most are temporary neuropraxias.
Only 10% will have permanent disability.
Erb’s palsy is commonest- C5- C6
Klumpke’s rarely- C8-T1
Who are more at risk of developing shoulder dystocia?
There are pre-labour factors and intrapartum factors.
How would you prevent SD?
Diabetes mellitus-
- Babies born to DM mothers have 2-4 fould increased risk (6.5 RR) of developing shoulder dystocia compared to same weight babies born to non DM mothers.
- In GDM, fetus has high shoulder, chest and abdominal ratios. So more prone to SD even in the absence of macosomia.
- Early IOL at 38weeks reduces SD in pre-exsisting DM/GDM .
- Elective CS should be offered for DM+ Macrosomia >4.5kg to prevent SD.
- 443 elective CS will prevent one permanent BPI.
Macrosomia without DM
- Macrosomia is when EFW> 4kg.
- 48% of SD occur in babies without macrosomia. Positive predictive value is only 3.3%.
- IOL does not prevent SD at delivery in macrosomic babies of non DM mothers.
- 2345 of additional CS will be needed to perform to prevent one permanent BPI. So not cost effective. Not recommended.
Maternal obesity
There is a relative risk of 2.3 of shoulder dystocia in women with a pre-pregnancy weight of more than 82 kg.
Previous history of shoulder dystocia.
- There is a 10 times higher risk of SD in a mother who has a past history of SD compared to general population.
- Offering CS section is not mandatory. Should be discussed with mother.
- Elective CS is preferable if past incident caused poor neonatal outcome/perineal trauma.
To whom you would offer elective CS to prevent SD?
- DM with macrosomia >4.5kg
- Previous history of SD with bad neonatal outcome/ perineal tears.
- Macrosomia > 4.5-5kg with no DM considering other factors.
Management
How you would diagnose SD?
I would look for signs of SD in all births where it is anticipated.
- ‘Head bobbing’ – this is when the head consistently retracts back between contractions during the active second stage
- Difficult delivery of the face and chin
- ‘Turtle-sign’ – the delivered head becomes tightly pulled back against the perineum and there is difficulty delivering the chin
- Failure of restitution of the head
- Shoulders fail to descend.
Management
About the Author
