Shoulder Dystocia Incidence

Although the definition of shoulder dystocia is the same among obstetricians, what differs among the medical professionals is the incidence of the potential life-threatening birth delivery issue.

How Common is Nerve Damage to the Shoulder?

Reports compiled from several studies performed in a number of countries place the incidence of shoulder nerve injuries between 0.3% and 1.5%. A few studies list the incidence of the medical problem both higher and lower than the 0.3% to 1.5% range. The actual incidence of shoulder nerve damage depends on the definition given to it by obstetricians, as well as how it is reported. For example, the Bulletin on shoulder dystocia issued by the American College of Obstetricians put the incidence at the higher end of the range at a little more than 1.4% of infant deliveries. However, the incidence of the medical disorder in Great Britain as presented by the Royal College of Obstetricians sits at the low end of the range (0.6%). A study performed by Chauhan in 2014 states the rate of infant shoulder nerve injuries at around 1.4%.

Why the Differences?

The most prevalent variable that causes the differences in the reported incidence of shoulder dystocia is the accuracy of the studies that present the numbers. Because of potential medical liability or malpractice, many obstetricians refuse to report on the delivery notes taken that verify the presence of shoulder nerve damage. This is especially true in the United States, where medical malpractice lawsuits have skyrocketed over the past 10 years, many of which made claims of doctor negligence during infant deliveries. Some of the studies add a declaration that states between 25% and 50% of infant shoulder nerve injury cases go unreported, which if accurate, would increase the rate of the medical disorder almost two times its currently reported rate.

Another reason for the inaccurate reporting of infant shoulder nerve damage incidence is how obstetricians define the medical emergency. Some obstetricians report the medical disorder only when they implement maneuvers to subtly move an infant’s shoulder or shoulders. On the other hand, many obstetricians report infant shoulder injuries if they witness even the slightest delay in the appearance of an infant’s shoulder from the birth canal. A few obstetricians report shoulder dystocia after witnessing an injury to the infant.

Another factor to consider involves the delivery group studied by any of the organizations that research the rate of the medical issue. Any study that includes an above average number of diabetic women or mothers who possess macrosomic neonates will skew study results much higher than the 1.5% incidence rate reported on the upper end of the range. Moreover, the presence of larger than average infants also produces research results that report a higher incidence of shoulder damage. This brings us to our final point: infants have grown larger over the past 20 years. Does this mean the high end of the incidence range at 1.5% needs to be pushed higher? Researchers need to perform more studies that account for the larger than average infant trend. Larger and heavier than average babies put mothers at a higher risk of experiencing shoulder dystocia.