Shoulder dystocia: Unpredictable and unpreventable

Shoulder dystocia is a known complication of vaginal delivery that can be extremely challenging to manage, mostly because it is unpredictable and unpreventable. It happens when the fetal head delivers but the shoulders do not with normal maneuvers.  It is one of the few emergencies encountered during labor that an urgent cesarean delivery or surgery cannot correct.

Hence, shoulder dystocia needs to be remedied with the maneuvers that the obstetrician is already trained in, according to a presentation at the 2018 Annual ACOG Meeting in Austin. Simulation and team training can also lessen some of the anxiety surrounding the event.

Incidence of shoulder dystocia ranges between 0.2% and 3%. “This wide range is due to subjectivity at the time of delivery as to what constitutes a shoulder dystocia,” said Amy Mackey, MD, ob/gyn residency program director at Abington Hospital-Jefferson Health in the Philadelphia area. “The definition that most people follow is a difficult shoulder delivery that does not resolve with gentle downward traction and requires additional obstetric maneuvers.”

A previous shoulder dystocia during delivery is the strongest risk factor. Other risk factors include operative delivery, maternal obesity, maternal diabetes, fetal macrosomia, a prolonged second stage and a precipitous delivery.

However, about 45% of deliveries with shoulder dystocia do not have any risk factors present, according to Dr. Mackey. “But even with risk factors, it does not predict who is going to have a shoulder dystocia and who is not,” she said.

When encountering a shoulder dystocia, the positioning of the mother is the first consideration. “The patient should be brought down on the bed, so that the bed does not obstruct your ability to perform gentle, downward traction,” Dr. Mackey told Contemporary OB/GYN. “Also, make sure you have a stool in the room and that you have someone ready to exert suprapubic pressure. That team effort is really important, so preparation is key.”

In addition, the axis of the force applied for downward traction is important to decrease the strain on the brachial plexus.

Dr. Mackey said it is important not to panic when a shoulder dystocia is encountered. “Force is measured in newtons, which has an exponential time component in the denominator,” she said. “The faster you apply pressure to the baby’s neck, the greater the force will be on the brachial plexus. Therefore, slow and gradual increase in pressure will be better tolerated by the fetus.”

Some physicians advocate delivering the posterior arm after performing the McRoberts maneuver and suprapubic pressure as better than rotational maneuvers to alleviate shoulder dystocia. “But this is controversial,” said Dr. Mackey. “It really depends on the clinical situation.”

Dr. Mackey said the order of the maneuvers is less important than having a standardized approach. “You want everyone in the room to be able to anticipate what will happen next,” she said. “For us, the provider repeats all the maneuvers. If the provider is still unsuccessful at achieving delivery, a second provider tries.”

Dr. Mackey said obstetricians should never exert fundal pressure. “There is a higher incidence of permanent brachial plexus injury if you use fundal pressure at the time of a vaginal delivery with shoulder dystocia,” she said.

An alternative maneuver is to place the mother on all fours.  “This is called the Gaskin maneuver, which is difficult to do with an epidural,” said Dr. Mackey.

The abdominal rescue procedure as opposed to the Zavanelli maneuver should be considered in difficult cases for which other obstetric maneuvers have failed. “This consists of a provider who delivers the baby vaginally while a second provider starts a C-section,” said Dr. Mackey. “Direct pressure is then applied to the shoulder to dislodge it from behind the pubic symphysis.”

Maneuvers performed for shoulder dystocia are intended to prevent hypoxic injury to the baby. “The time that you have from the time you encounter shoulder dystocia to the time that the baby needs to be delivered is variable, based on the status of the baby going into the delivery,” said Dr. Mackey. “For example, if you have a baby that is well oxygenated, you are going to have more time than if you have a baby that is borderline to relieve the shoulder to prevent hypoxic injury.”

Documentation is essential when a shoulder dystocia is encountered.  The time the fetal head delivers should be recorded for all deliveries and the time the shoulders deliver should be recorded in all cases of shoulder dystocia. “You also want to document which shoulder is anterior because there are cases of brachial plexus injury of the posterior shoulder,” said Dr. Mackey. “This occurs when the posterior shoulder is obstructed by the sacral promontory.”

Once a shoulder dystocia is resolved, the obstetrician must stay alert to postpartum complications. “Postpartum hemorrhage and third- and fourth-degree lacerations are increased in women who experience a shoulder dystocia,” said Dr. Mackey.

Disclosures:

Dr. Mackey reports no relevant financial disclosures.