Objective
We sought to objectively evaluate the amount of force applied during deliveries complicated by shoulder dystocia among different providers.
Study Design
Providers who do deliveries at our institution were approached for participation. The simulation exercise used a childbirth mannequin that measures the amount of force the provider applies to the fetal head during delivery. The amount of force applied and information regarding the provider’s level of experience, height, weight, and gender was recorded. This study was approved by the hospital institutional review board.
Results
A total of 47 providers participated. The mean force applied during each situation was not associated with the provider’s experience, height, weight, or gender.
Conclusion
Provider experience, gender, and body habitus were not associated with the amount of force applied during delivery. We found differences between family medicine and obstetrics/gynecology providers. In addition, a significant number of all providers (19/47, 40%) pulled >100 N.
Shoulder dystocia occurs when the anterior fetal shoulder becomes impacted behind the pubic symphysis. This complication occurs in up to 2% of all vaginal deliveries and may be associated with significant long-term complications to include brachial plexus injuries, clavicular fracture, hypoxic brain injury, neonatal death, and significant maternal lacerations.
There are several studies that have begun to explore the forces applied to the fetal head and neck during different delivery scenarios, both simulated and real, in an effort to better understand and manage the emergency of shoulder dystocia. Albeit a rather arbitrary cutoff, 100 N has generally been accepted as the maximum force that should be applied during a delivery. This number comes from a study done by Allen et al that demonstrated that 99.89 N of force resulted in a brachial plexus injury and clavicular fracture in 1 delivery complicated by shoulder dystocia. A recent United Kingdom study by Crofts et al used a mannequin to evaluate forces applied by midwives and physicians during a simulated shoulder dystocia scenario. Delivery, which in their study required delivery of the posterior arm, was achieved in only 42.5% of the simulations prior to training. Forces that exceeded 100 N were used in two-thirds of the simulations. This study would suggest that specific training in management of shoulder dystocia might enable providers to use maneuvers rather than resorting to increased forces to resolve a shoulder dystocia.
Because of the significant differences between obstetric practice and providers in the United States vs the United Kingdom, most notably the greater prevalence of midwives for routine deliveries, we undertook this study to evaluate the forces applied during spontaneous vaginal delivery and those complicated by shoulder dystocia in our provider population. Our study was also designed to take into account additional variables that could potentially influence the amount of force applied to include a provider’s specialty, level of training, personal experience with this emergency, gender, and body habitus.
Materials and Methods
This protocol was approved by the hospital institutional review board. Providers at Madigan Army Medical Center who regularly perform deliveries, to include obstetrics and gynecology staff, obstetrics and gynecology residents, certified nurse midwives, family medicine staff, and family medicine residents, were recruited for the study either during normal departmental morning report or scheduled academic time. Informed consent was obtained prior to enrollment.
A commercially available childbirth simulator (PROMPT birthing trainer; Limbs and Things Ltd, Bristol, United Kingdom) was used, which measures the force in newtons applied to the infant’s head during delivery. This simulator and the internal force measurement mechanism have been described in detail in a previous publication. The mannequin was positioned on an examination table either in clinic or on labor and delivery. Prior to beginning the simulation, investigators recorded information about the following for each participant: gender, height, weight, body mass index (BMI), number of deliveries performed, number of shoulder dystocias managed, practice specialty, and level of training.
Participants were allowed to sit or stand as they usually do during a delivery; they were also allowed to adjust the examination table to their preferred height. The infant head was always placed in the left occiput anterior position ( Figure 1 ). Participants were advised not to expect descent of the fetus or resolution of the dystocia, as the purpose of the study was not to achieve delivery but to determine how hard they believed they normally pulled on the fetal head during the situations presented. Participants were instructed to pull as hard as they usually do: (1) during a normal vaginal delivery, (2) to diagnose a shoulder dystocia, (3) with application of McRoberts position and suprapubic pressure to resolve a shoulder dystocia, and (4) prior to abandoning attempts at vaginal birth and performing the Zavanelli maneuver. The peak force for each of these pulls was then added together to calculate the total peak force applied, which was included to determine if there was any summative difference that might not be seen between the individual pulls. These 4 scenarios were explained to participants before starting the simulations. After simulation was completed, feedback was given to the participants regarding how hard they pulled in each situation. An example of the feedback output recorded by the software can be seen in Figure 2 .
