Shoulder Dystocia - Lippincott Williams & Wilkins

Shoulder Dystocia 15
death. Maternal morbidity following shoulder dystocia
can include postpartum hemorrhage, perineal lacerations
and bruising, and pelvic hematoma.
SHOULDER DYSTOCIA CAUSES
When weight exceeds 4000 g, the fetal body assumes
more adult proportions with the width of the fetal
shoulders exceeding the biparietal diameter of the
head. The fetal head is born but the anterior shoulder
becomes trapped behind the symphysis pubis or
the posterior shoulder catches on the sacral promontory.
Stretching of the brachial plexus can happen during
maternal pushing, during vacuum extractor or forceps
use, or during birth hand maneuvers. Stretching
of the brachial plexus nerves can cause a temporary
nerve conduction deficit called neuropraxia. 4,5 Severe
stretching may avulse brachial plexus nerve roots from
the spinal cord causing permanent loss of arm function.
Cervical nerves 5 through 8 and T1 may be involved.
Future function of the fingers, hand, and arm will depend
on which nerves are damaged.
The clavicle or humerus may fracture during attempts
to relieve the shoulder dystocia. These are temporary
injuries and heal with splinting of the arm. An
arm is splinted by positioning it across the chest with
the hand resting under the opposite shoulder, held in
place with a Velcro strap or a length of fabric wrapped
around the trunk and pinned in place.
Brachial plexus injury is the morbidity most often
associated with shoulder dystocia and is a common
source of liability claims. 6 The incidence of brachial
plexus injury ranges from 0.4 to 1.5 per 1000 births. 7,8
Fifty percent of brachial plexus injuries occur without
shoulder dystocia. 1 Brachial plexus injuries have occurred
after cesarean delivery. 1 Brachial plexus injuries
to the posterior shoulder have also been documented. 1
Postcesarean and posterior arm injuries raise the question
of the relationship of maternal pushing efforts to
the stretching of the brachial plexus.
Most newborns recover spontaneously from brachial
plexus injury with physical therapy. 7 Only 5% to 22% of
infants have permanent injury. 7,8 Spontaneous elbow
flexion at 3 months is a favorable sign for recovery without
corrective surgery. 8 Infants who need surgical repair
rarely have full return of neurologic function. 9
Shoulder dystocia with permanent arm or brain injury
or newborn death is a frequent source of malpractice
claims. 6,10 Nurses working together with other professionals
during prenatal and intrapartum care can reduce
the incidence and improve the outcomes of shoulder
dystocia (Table 1).
ANTENATAL EDUCATION TO DECREASE
SHOULDER DYSTOCIA RISKS
Nurses are an important source of health information
for expectant mothers. The office nursing staff may
provide the most care continuity for women as obstetricians
and midwives rotate between the prenatal
office and labor and delivery. Three risk factors for
shoulder dystocia—obesity, excessive prenatal weight
gain, and diabetes—are all related to another risk factor,
macrosomia. 1,10
Weight management
With 30% of American childbearing-age women obese
before pregnancy, 14 weight management education
may be the most important tool a nurse can provide
to reduce the threat of shoulder dystocia. Assess overweight
and obesity at the first prenatal visit. An accurate
height and weight measurement is an essential
part of the prenatal record. Measuring height, preferably
with a stadiometer (a wall mounted height measure),
is more accurate than maternal height recall.
Body mass index (BMI) graphs, calculation wheels, or
computer calculator programs should be readily available.
Many adult women have never had their BMI calculated.
This presents the nurse with an opportunity
to teach how excess weight can influence pregnancy,
the birth, and the future health of both mother and
infant.
Body mass index determination offers a more precise
measure of weight related to height and is most
useful in advising an adequate but not excessive prenatal
weight gain. 15,16 The Institute of Medicine issued
recommended prenatal weight gains in 1990 that are
based on pregravid BMI (Table 2). 11 Women of normal
weight, for example, are advised to gain 25 to 35
lb for a healthy pregnancy and obese women at least
15 lb. Using these tailored recommendations helps
women avoid unnecessary weight gain, which predisposes
them to a macrosomic infant and maternal obesity
in later life.
The recommended weight gain should be documented
on the prenatal record so that all prenatal care
providers use the same reference point. A maternal
BMI of 30 or more should be documented on the prenatal
record problem list as obesity is a risk factor
for many perinatal problems, including gestational diabetes,
preeclampsia, stillbirth, macrosomia, prolonged
labor, shoulder dystocia, and cesarean section. 1,10 Documenting
BMI indicates more about the risks of obesity
than the labels obese or morbidly obese.
Weight gain should be measured at each prenatal visit
and assessed for adequacy. Graphs are available that