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Shoulder dystocia needs to
be distinguished from a mere difficulty with delivery
of the shoulder. The latter occurs because of the prevailing
delivery practice, with the mother in a semi-recumbent
position on the delivery bed. There may be insufficient
room for appropriate lateral i.e. downward flexion
for delivering the anterior shoulder. In addition,
the weight of the mother is in part taken on the sacrum
which is therefore pushed upwards, thus decreasing
the antero-posterior diameter of the pelvic outlet.
Many of these cases require only a positional change,
into left lateral, or kneeling, which frees the sacrum
and allows lateral flexion.
Proper shoulder
dystocia occurs when there is disproportion between
the bisacromial diameter of the fetus and the anterioposterior
diameter of the pelvic inlet. This results in the
anterior shoulder becoming impacted behind the symphysis
pubis ( 1)
| RISK FACTORS FOR SHOULDER DYSTOCIA (2)
Prepregnancy:
Maternal birth weight
Prior shoulder dystocia*
Prior macrosomia
Pre-existing diabetes
Obesity**
Multiparity
Prior gestational diabetes
Advanced maternal age
Antepartum:
Excessive maternal weight gain***
Macrosomia
Short stature
Postdatism
Intrapartum:
Prolonged second stage
Protracted descent
Failure of descent of head
Abnormal first stage
Need for midpelvic or assisted delivery
* Reccurrence rate of between 10-13.8% (3,4)
** Mothers that weigh more than 81kg experience
30% of all shoulder dystocias(5)
(RR x8) (6)
*** More than 20kg gain showed an increase in shoulder
dystocia from 1.4% to 15.2% (7)
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Diabetic mothers have a threefold increased risk of
shoulder dystocia because of a disproportionate increase
in fetal abdominal circumference to head circumference
(8).
The presence of maternal diabetes together with macrosomia
(defined here as > 4kg) is estimated to result in
shoulder dystocia in a third of those delivering vaginally
(9)
However, the event is difficult to predict, as half
of all instances of shoulder dystocia occur in babies
weighing less than 4kg (10).
Furthermore, of the babies which do weigh over 4 kg,
most are not detected as such clinically. Even an ultrasound
scan often misses these babies because of its low sensitivity
(60%) of detection of macrosomia in the third trimester
(8).
Inducing the suspected large babies only increases
the intervention rate and will not decrease the incidence
of shoulder dystocia (11).
A policy of caesarean sections for those babies predicted
antenatally to weigh more than 4.2 kg increases the
section rate but does not have a significant impact
on the rate of shoulder dystocia (11).
A prophylactic caesarean section policy on babies of
4-4.5kg would require more than a thousand sections
to avert one brachial
plexus injury (8).
| 5th CESDI report
56 cases were reviewed in 1996 which resulted
with the death of the baby. The focus group
found 66% of cases to have Grade
3 suboptimal care where a "different
management could reasonably have been expected
to have altered the outcome". 36% of the
babies were born to primigravidas and although
40% were predicted to be large babies, these
were often not flagged up as potential problems.
Maternal obesity was noted, with 11% of the
mothers having a BMI of > 40. The overall
induction rate was 36%.
Conclusions :
- Anticipate the problem, look out for signs
and risk factors
- Senior staff (including paediatricians)
should be called immediately. Guidelines
should make this clear
- McRoberts manoeuvre should be carried out
with suprapubic pressure
- Failure of the above means it is reasonable
to carry out the all fours manoeuvre or squatting
positions if obstetric assistance is not
yet available
- The next step is delivery of the posterior
shoulder
- Complete and accurate notekeeping is crucial
- Regular updates on the local protocols
is helpful
- Staff should be aware of the procedures
of symphysiotomy, clavicular fracture and
/or the Zavenelli procedure if desperate
measures are called for.
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If we are unable to avoid this emergency, it is vital
to be clear on the management of shoulder dystocia
in order to act quickly and efficiently. Adequate training
and guidelines are essential.
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SUGGESTED MANAGEMENT OF SHOULDER
DYSTOCIA
1. Early recognition / raised
level of suspicion:
Large baby, post dates, large
maternal BMI, maternal diabetes,
previous history of shoulder dystocia;
prolonged 2nd stage, turtle neck
sign
2. Call appropriate staff:
- Senior midwife
- 2nd midwife
- senior obstetrician
- anaesthetist
- paediatrician
- Explain to the patient and family
what is happening
3. NB
Is this a proper shoulder dystocia,
or is it caused by maternal posture,
with sacrum pushed up, leaving
not enough room at the outlet?
In this case consider left lateral
position, or, (in the absence of
an epidural), squatting or kneeling
(all fours). (12)
4. Mc Roberts position:
Femora are abducted, rotated outwards
and flexed, so that thighs touch
the mother's abdomen, with the
aid of two assistants. The buttocks
need to come over the edge of the
bed, allowing the sacrum to rotate
backwards.
Apply suprapubic pressure: Another
assistant puts hand laterally and
pushes in direction that the baby
is facing and posteriorly to try
and disimpact the anterior shoulder.
This is done at the same time as
moderate traction of head. 91%
of cases will be delivered by this
stage (13).
5. Make or enlarge episiotomy:
This enables access to the vagina
for step 6 or 7
Please note: there is NO place
for fundal pressure or undue traction
on the head. The brachial plexus
is already under stretch and further
traction results in neurological
damage. Fundal pressure can only
increase impaction of the shoulder
under the symphysis pubis (10).
6. Woods screw manoeuvre:
Rotation of the posterior shoulder
by 180 degrees to deliver the anterior
shoulder from under the symphysis
pubis (14).
Rubin's manoeuvre is turning the
baby in the opposite direction
(reverse Woods manoeuvre). This
has the advantage of abducting
the shoulders, thereby decreasing
the diameter (15).
OR
7. Delivery of posterior arm:
insert hand into sacral hollow
to identify the posterior shoulder,
arm down to the wrist. Sweep this
across the fetal chest, flexing
the elbow, to deliver the arm posteriorly.
8. Zavanelli manoeuvre (cepahalic
replacement):
Manual return of the partially
born, but undeliverable, fetus
to the vagina for extraction by
caesarian section (16).
This is done by rotating the head
back to the occiput anterior position,
flexing the head with pressure
on the occiput whilst using the
other hand to replace the chin
back into the vagina. Tocolytics
can help the procedure (terbutaline
0.25mg sc)
OR
Symphysiotomy:
division of the fibrocartilagenous
symphysis pubis (17).
Using local anaesthetic, infiltrate
the joint with the patient in the
lithotomy position (thighs supported
at no more than 90 degrees, so
as not to put too great a strain
on the sacroiliac joints). Use
the index and middle fingers of
the left hand on the posterior
aspect of the symphysis. Push the
indwelling catheter aside with
the index finger and use the middle
finger to monitor the action of
the scalpel. The latter is used
like a pencil, keeping it vertical
and, using the entry point as a
fulcrum, to bring the blade down
towards the operator. Remove, turn
180 degrees and in original point
to divide the upper half of the
symphysis. If completed, the middle
finger can fit into the space created
by the separation.
Step 8 is only if all the above
manoeuvres have failed. The CESDI
recommendations state that clinicians
should be aware of these if desperate
measures are sought. We are unlikely
to see an RCT in either procedure.
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Important to have accurate record
keeping:
- Time head delivered
- Time each manoeuvre was performed
- Time body delivered
- Staff present
- Need for regular scenario training
and ward drills
Regular audit of shoulder dystocia
cases, irrespective of the outcome
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References:
1. Roberts L. Shoulder dystocia. Progress in Obstetrics
and Gynaecology. Volume 11: chapter 12:201-16.
2. O'Leary JA, Leonetti HB. Shoulder dystocia: Prevention and treatment. Am
J Obstet Gynecol 1990;162:5-9, Abstract
3. Smith RB. Shoulder dystocia: what happens at the next delivery? Br J Obstet
Gynaecol 1994;101:713-5.43, Abstract
4.Lewis, Recurrence rate of shoulder dystocia. Am J Obstet Gynecol 1995;172(5):1369-71, Abstract
5. Seigworth G. Shoulder dystocia. Obstet Gynecol 1966;28:764-7.
6. Schwartz B. Shoulder dystocia. Obstet Gynecol 1958;11:468-71.
7. Boyd ME, Usher RH. Fetal macrosomia: prediction, risks, proposed management.
Obstet Gynecol1983;61:715, Abstract
8. Rouse D. Prophylactic caesarean delivery for fetal macrosomia diagnosed
by means of ultrasonography - a Faustian bargain? Am J Obstet Gynecol 1999;181:332-8, Abstract
9. Johnstone F. Shoulder Dystocia. Br J Obstet Gynaecol 1998;105:1256-61, Abstract
10. CESDI 5th Annual Report published by the Maternal and Child Health Research
Consortium in May 1998.
11. Weeks J. Fetal macrosomia: does antenatal prediction affect delivery route
and birth outcome? Am J Obstet Gynecol 1995;173:1215-9, Abstract
12. Luria S. The ABC of shoulder dystocia management. Asia-Oceania J Obstet
Gynaecol 1994;20:195-7, Abstract
13. Woods CE. A Principle of physics as applicable to shoulder delivery. Am
J Obstet Gynaecol 1943;45:796-804.
14. Rubin A. Management of shoulder dystocia. JAMA 1964;189:835.
15. Bruner JP. All-Fours Maneuver for reducing shoulder dystocia during labor.
J Reprod Med 1998;43:439-43, Abstract
16. Sandberg E. The Zavanelli Maneuver: 12 years of recorded experience. Obstet
Gynecol 1999;93:312-7, Abstract
17. Menticoglou SM. Symphysiotomy for the trapped aftercoming parts of the
breech: A review of the literature and a plea for its use. Aust NZ J Obstet
Gynaecol 1990;30:1-9, Abstract
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