What is shoulder dystocia in labor and why is it a concern?

Shoulder dystocia is an obstetric emergency that requires maneuvering for resolution. Read more about its repercussions.

Written and verified by the doctor Mariel mendoza on October 29, 2021.

Last update: October 29, 2021

Shoulder dystocia is a complication of labor rare, unpredictable and with high morbidity for both mother and baby. Its resolution requires specific maneuvers to detach the child’s shoulders.

Death of the baby at birth is very rare, but the morbidity associated with complications is the worrying factor. Complications can range from damage to the brachial nerve plexus, a fracture of the humerus or clavicle, to neurological damage due to a deficiency in arterial circulation to the brain.

It is an obstetric emergency that requires prompt diagnosis and care by the specialist, since the time to perform the maneuvers and extract the baby without collateral damage is limited.

What is shoulder dystocia?

Clinically, the situation is identified when there is difficulty for the baby’s shoulders to spontaneously cross the pelvis after the expulsion of the head has already occurred. However, by definition, true dystocia is one that requires maneuvering to detach the shoulders, in addition to downward traction and an episiotomy.

It is considered that more than 1 minute must elapse between the expulsion of the head and the exit of the shoulders to be considered a shoulder dystocia.

These resolution maneuvers range from simple to complex, inside the vagina and outside the vagina. They must be done sequentially and by qualified personnel.

Worldwide, the incidence is estimated between 2% to 3% of pregnancies. However, it is not an exact value, since in many cases it is resolved with preventive maneuvers and the diagnosis is not made. This is due to the application of the pressure maneuver on the pubis, which is one of the preferred to detach the shoulder.

The prevalence of the disorder is 2-3%, but it could be higher due to lack of diagnosis.

How is it identified?

There is a major clinical sign called turtle sign, which allows to identify shoulder dystocia. This sign appears when, after the fetal head has emerged, it recedes during the maternal push and overlaps against the perineum, as if trying to re-enter the vaginal canal.

Shoulder dystocia can be one-sided or both. In either circumstance, traction on the fetal head when it is ejected does not cause the shoulders to dislodge.

This causes elongation of the cervical nerves of the brachial plexus, which can lead to paralysis of the baby’s upper arm or forearm.

Risk factors associated with shoulder dystocia

Risk factors for shoulder dystocia are divided into maternal history, antepartum factors, and intrapartum factors. They are all related to each other. Nevertheless, about 50% of cases are seen in patients with no known risk factors.

Maternal history

  • History of shoulder dystocia or baby with brachial plexus injury in previous deliveries.
  • Maternal obesity (with a body mass index greater than or equal to 30).
  • Pregestational maternal diabetes.
  • Multiparity (having had multiple children).
  • Advanced maternal age.

Antepartum factors

  • Macrosomia: estimated fetal weight greater than or equal to 4500 grams by ultrasound or birth weight greater than or equal to 4000 grams.
  • Gestational diabetes.
  • Excessive maternal weight gain during pregnancy: equal to or more than 20 kg.
  • Chronologically prolonged pregnancy: more than 42 weeks’ gestation.

Intrapartum factors

  • Maternal pelvic abnormalities: pelvis with android or anthropoid features and large fetal weight for gestational age.
  • Precipitated or instrumental delivery.
  • Abnormal progression of labor.
  • Expulsive period of failed, prolonged or stopped labor.

Impact of shoulder dystocia

The repercussions of shoulder dystocia can be analyzed in those that affect the mother and those that are specific to the baby. Let’s see in detail.

Impact on the baby

The main concern is neonatal hypoxia, because during shoulder dystocia the blood flow through the umbilical cord is occluded by compression. Oxygen deficiency creates brain problems that lead to neurological damage.

The maximum time to deliver the baby is considered to be 7 to 8 minutes to avoid neonatal hypoxia.

The most frequent complications are brachial plexus injury (prevalence 60%), clavicle fracture (20-30%) and humerus fracture (5-10%). Brachial plexus injury is caused by excessive traction used by both the baby and the operator in attempting to remove the shoulder.

When it generates important affectation there may be paralysis of the shoulder, arm, or wrist muscles. This is manifested with a hanging arm with the elbow extended or the claw position of the hand. It does not usually require surgery, but rather orthopedic measures.

Maternal repercussions

The consequences for the mother are variable, although very rare. They include tears of the birth canal, postpartum hemorrhage, inflammation of the endometrium, rupture of the uterine walls, and loss of bladder tone.

Some maneuvers reduce the incidence of labor dystocia, although they are reserved for cases with risk factors.

What to do in the event of a diagnosis of shoulder dystocia?

The most important thing is the early recognition of the disorder. The maneuvers are sequential and range from the simplest to the most complex.

Pressure is first performed above the pubis and other maneuvers outside the vagina that do not require anesthesia. If the shoulder cannot be dislodged, the episiotomy cut should be prolonged to allow expulsion of the head.

In the latter case, the fetal head must be restored within the vagina for a cut to the pubic symphysis or an emergency cesarean section. Exerting pressure on the abdomen, uncontrolled maternal pushing, and traction of the fetal head are contraindicated.

It is not possible to prevent shoulder dystocia, since there are no definitive predictors. Risk factors only predict 15% of circumstances.

In addition, it is not possible to know the true weight of the baby before its birth or the diameter of the maternal pelvis through which the fetus will descend. So you cannot know if it will occur until the time of labor.

For this reason, scheduled cesarean section is not appropriate in cases of estimated fetal weight by ultrasound greater than 4500 grams. Surgical indication is reserved as a preventive measure when the estimated fetal weight is greater than 5000 grams in patients without diabetes and greater than 4500 grams in patients with diabetes.

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