The maternal model - composed of pleather "skin," carpet foam, foam sealer and other components - features a birth canal, a mock uterus connected to a pneumatic pump to simulate the natural pattern of uterine contractions and force from a mother's pushing, and flexible legs that can be moved to rotate the pelvis.
The fetal model consists of a cloth mannequin outfitted with a joystick device, a spring and wooden dowels representing the cervical vertebrae. Additional elements measure neck extension, rotation and stretching of the brachial plexus nerves during delivery.
To deliver the "baby" during the study, Gurewitsch wore a force-sensing glove. The custom, nylon-lycra glove has pockets sewn into it to house force-sensors, which were used to measure the traction she used in delivery. Wires emanating from the sensors connected to a computer-based data-acquisition system that stored and processed the data.
Gurewitsch performed 10 deliveries by turning the baby so its spine faced the mother's belly, 10 deliveries by turning the baby so its spine faced the mother's spine, and 10 deliveries by moving the mother's legs back.
The first maneuver was associated with the least amount of force, at 6.5 pounds, to the baby's head necessary to achieve delivery. The other techniques applied 8.5 pounds and 16 pounds, respectively. The first maneuver also produced the least amount of stretching on the baby's brachial plexus nerves, at 2.9 millimeters. The other techniques caused the nerves to stretch by 6.9 millimeters and 7.3 millimeters, respectively.
Researchers calculated that turning the baby created as much as 2 centimeters of extra space between the baby's shoulders and the mother's pubic