Related Experiment Video
Updated: May 31, 2026

An Instrumented Pull Test to Characterize Postural Responses
Published on: April 6, 2019
A device that measures the pulling force and vector of delivering a baby
1Department of Obstetrics and Gynecology, Penn State College of Medicine, Hershey, PA, USA. peisnerd@alumni.caltech.edu
Objective:
I sought to demonstrate a new device that measures the pulling on an infant during a vaginal delivery.
Study Design:
The Peisner Platform (US Patent 6,684,165; Canadian patent 2,436,154) utilizes Newton's Third Law to measure the force/vector of delivering a baby. Ten patients at term with a singleton fetus in the vertex presentation were recruited for this pilot study. The platform measured the forces/vectors on the fetal head during the delivery. The primary outcomes were the graphs of the force/vector on the fetus and duration of that force.
Results:
The pulling force exerted on the fetus ranged from 31.7-135.4 N over 8-51 seconds. Force vectors were often negative early, and positive later.
Conclusion:
This new device, which measures the pulling force and vector of delivering a baby, has been successfully demonstrated.
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