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Updated: Jul 13, 2026

Biaxial Basal Tone and Passive Testing of the Murine Reproductive System Using a Pressure Myograph
Published on: August 13, 2019
Pattern and degree of forces applied during simulation of shoulder dystocia
Joanna F Crofts1, Denise Ellis, Mark James
1Department of Obstetrics and Gynecology, North Bristol NHS Trust, Southmead Hospital, Bristol, UK. jocrofts@doctors.org.uk
Objective:
The objective of the study was to determine the level and pattern of forces applied during simulated shoulder dystocia.
Study Design:
One hundred forty staff (95 midwives, 45 obstetricians) were randomized from 6 UK hospitals. Applied delivery force was measured during a standardized simulated shoulder dystocia. Maximum, average, total, and applied force gradients were calculated for each delivery.
Results:
There was a wide range for all force variables: geometric mean maximum applied force 106 newtons (N) (range 6 to more than 250, n = 113), maximum force gradient 45 N/s (range 2-249, n = 113), total applied force 2954 N/s (range 33 to 14,197, n = 108), and average applied force 16 N (range 0-68, n = 108).
Conclusions:
Despite participants managing the same scenario, there was great variation in the pattern and degree of traction used. High forces were applied during two thirds of simulations. Training must emphasize that maneuvers should be used to overcome shoulder dystocia while minimizing iatrogenic applied force.
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