When the anterior shoulder impacts against the symphysis pubis after the baby's head is born, preventing further descent of the baby.
Defined as a birth that requires additional manoeuvres to deliver the fetal shoulders after a normal gentle traction has failed.
A rare but serious obstetric emergency where the midwife needs to act promptly.
Why does shoulder dystocia occur (in anatomical terms)?
It occurs as a result of disproportion between the bisacromial diameter of the fetus and the anteriposterior diameter of the pelvic inlet (11cm) compared to the roomier oblique diameter (13cm).
Usually the posterior shoulder has descended past the sacral promontory and entered the true pelvis. The anterior shoulder starts to descend into the pelvis but becomes impacted behind the symphasis pubis. Rarely, the posterior shoulder gets stuck behind the sacral promontory.
No amount of tugging or cutting of episiotomy will release the bony obstruction (not a soft tissue issue).
What is 'bed' dystocia?
This occurs when a woman is propped up on the bed and the baby's head is born down into the mattress. This causes the sacrum to be pushed inward (due to the weight of the mother), decreasing the anteriposterior diameter of the pelvic outlet, and there may be insufficient room for lateral flexion to allow delivery of the anterior shoulder.
Changing the woman's position in this case (to all fours, standing or rolling into left lateral position) allows lateral flexion and easy birth.
What is the incidence of shoulder dystocia, and what are the risk factors?
'True' shoulder dystocia occurs in about 0.2-2.8% births.
Most cases are unanticipated - approximately half occur in the absence of any risk factors and without warning.
Maternal- increasing age
- maternal birthweight
- abnormal pelvic anatomy
- gestational diabetes
- prolonged pregnancy
- previous shoulder dystocia
- short stature
- suspected macrosomia (>4000g)
- assisted delivery (forceps/vacuum)
- protracted active phase of first stage of labour
- protracted second stage of labour
Why does assisted delivery (using forceps or vacuum extraction) increase the risk of shoulder dystocia?
Due to elongation of the head, extension of the neck, and abduction of the shoulders, which increases the bisacromial diameter of the fetal shoulders making entrapment behind the symphysis pubis more likely.
What are some of the warning signs of shoulder dystocia?
A prolonged second stage of labour; 'bobbing' of the fetal head during second stage (may indicate the fetal shoulders have not rotated); the 'turtle' sign after birth of the head (recession of head after it is born); congestion of the face; 'chubby' cheeks.
What are the three principles of management, for shoulder dystocia?
1. Increase the size of the functional bony pelvis (e.g. McRoberts manoeuvre).
2. Decrease the bisacromial diameter of the fetus (the breadth of the shoulders, e.g. suprapubic pressure).
3. Change the relationship of the bisacromial diameter within the bony pelvis (through internal manoeuvres).
What does a midwife require to manage a shoulder dystocia effectively?
- Focussed and calm environment.
- Take the lead to direct the team and ensure a coordinated approach.
- Knowledge and skills around principles and manoeuvres for management.
What does the HELPERR mnemonic stand for?
H - Call for help.
E - Evaluate for episiotomy (for internal manoeuvres)
L - Legs (McRoberts manoeuvre)
P - Pressure (suprapubic pressure)
E - Enter (internal rotation - Rubin, Woodscrew, & Reverse Woodscrew manoeuvres)
R - Remove posterior arm ('cat lick' manoeuvre)
R - Roll (Gaskin manoeuvre)
What is the McRoberts manoeuvre?
In a flat supine position (no pillows!) the maternal hips are flexed and abducted so that the thighs are on the woman's abdomen (knees to ears).
This position flattens the sacral promontory and results in cephalad rotation of the pubic symphysis.
What is suprapubic pressure (Rubin I)?
An assistant's hand is placed suprapubically over the fetal anterior shoulder, applying continuous pressure with a downward and lateral motion on the posterior aspect of the anterior shoulder, to disimpact it. If this is unsuccessful, a rocking motion can be applied.
It is important to accurately identify the plane of the fetal back as the midwife is attempting to adduct the shoulders and decrease the bisacromial diameter.
What is the Rubin II manoeuvre?
Two fingers are inserted into the vagina posteriorly. They are moved upwards to apply digital pressure to the posterior aspect of the anterior shoulder, pushing it towards the fetal chest.
This will adduct the fetal shoulder girdle, reducing it's diameter and rotating the shoulders towards the oblique diameter of the pelvis.
What is the Woodscrew manoeuvre?
While maintaining pressure on the posterior aspect of the anterior shoulder, the midwife introduces two fingers of her second hand into the vagina, locating the anterior aspect of the posterior shoulder. Nptj jamds apply pressure to rotate the posterior shoulder in the same direction as before.
This is to move the shoulders into the oblique diameter of the pelvis.
What is the Reverse Woodscrew manoeuvre?
The fingers on the posterior shoulder aare removed from the vagina and the two fingers on the anterior shoulder moved down and along the fetal back to the posterior aspect of the posterior shoulder.
This attempts to rotate the shoulder in the opposite direction to the Woodscrew manoeuvre.
What is the 'cat lick' manoeuvre?
Trying all fours may be helpful before trying this manoeuvre. Two fingers are inserted into the vagina and passed down the front of the posterior arm as far as possible to flex the arm at the elbow. The forearm is delivered in a sweeping motion over the fetal anterior chest wall.
DO NOT pull on the fetal arm - this may fracture the humerus.
Removing the posterior arm from the birth canal aims to shorten the bisacromial diameter, allowing the fetus to drop into the sacral hollow, freeing the impaction.
What is the Gaskin manoeuvre?
The woman is rolled into the all-fours position.
The shoulder may dislodge during the act of turning. Rotation of the woman may facilitate delivery by increasing the pelvic diameters and allowing better access to the posterior shoulder. Gravitational forces may also help to disimpact fetal shoulders.
What is the Running Start position?
The woman lifts the leg on the side of the baby's back, from an all-fours (Gaskin) position. Now the woman is in a position with one knee down and the other knee up, like a runner waiting for the signal to begin running.
What are the complications associated with shoulder dystocia?
- rectovaginal fistula
- symphyseal separation or diastasis
- femoral neuropathy
- 3rd or 4th degree tear
- uterine rupture
- brachial plexus palsy
- clavicle fracture
- permanent neurological damage
- facture of the humerus
What are the manoeuvres of last resort with a shoulder dystocia?
- Deliberate clavicle fracture
Upward pressure on midpoint f anterior fetal clavicle
- Zavanelli manoeuvre
Cephalic replacement followed by c-section
- General anaesthesia
musculoskeletal or uterine relaxation may bring about enough uterine relaxation to effect delivery
Intentional division of the fibrous cartilage of the symphysis pubis under local anaesthesia. Only used when all other manoeuvres have failed and c-section is unavailable
What does documentation of a shoulder dystocia require?
- Correct differentiation between 'difficult shoulders' and a shoulder dystocia (impacts subsequent pregnancies).
- All manoeuvres employed (outline what, how long each manoeuvre took, and their effect).
- Time taken to deliver baby.
- Woman should be fully informed about what happened.
- De-briefing or counselling offered.
What is the incidence of shoulder dystocia in babies who weigh between 4000g to 4500g?
5-9% in babies weighing 4-4.5kg.
0.6-1.4% in babies weighing 2500-4000g.
Equal frequency in primigravid and multigravid women.
The majority of shoulder dystocia's are caused by macrosomic babies. True or False?
Most cases are caused by babies of normal birth weight. Most babies with a birth weight of >4500g do not develop shoulder dystocia.
A protracted active first stage, a prolonged second stage with 'head bobbing' and instrumental delivery are all risk factors for shoulder dystocia.
True or False?
They are all intrapartum risk factors.
The protracted active phase of first stage usually shows as slow progress from 7-10cm.
A potential outcome for the baby from having shoulder dystocia is having Erbs Palsy or Klumpke palsy.
True or False?
True. 7-20% babies have brachial plecxus injuries.
- Erb's palsy (the 'waiter's tip') affects C5-6 nerve roots.
- Klumpke palsy affects C8-T1 nerve roots.
- Other outcomes may be fractured clavicle, fractured humerus, neonatal asphyxia.
An episiotomy is an effective method to assist birth of the shoulders when they are stuck.
True or False?
An episiotomy is only useful if internal manoeuvres are needed (to help create more space). Shoulder dystocia is a bony problem not a soft tissue problem.
Spontaneous separation of the symphysis pubis is a common occurence with a difficult shoulder dystocia.
True or False?
Spontaneous separation of the symphysis pubis is a potential outcome for women if manoeuvres are required to deliver the babies shoulders - but it is (fortunately) not a common occurrence.
What is the ALSO course?
Advanced Life Support in Obstetrics course.
What is the PrOMPT course?
Practical Obstetric Multi Professional Training course.
What does the HELP! MR SPARE mnemonic mean?
Help! Ask someone to call for an ambulance, or press the emergency bell if in hospital.
MR - McRoberts
SP - Suprapubic Pressure (Rubin I)
A - All fours
R - Remove posterior arm (while in all fours)
E - Enter for internal manoeuvres
What are three words that can help you remember how to manage shoulder dystocia?