Johns Hopkins researchers, using a novel birthing
simulator designed by biomedical engineering faculty, staff
and students, have identified what may be the least
forceful way to deliver a baby whose shoulders are stuck in
the birth canal.
Shoulder dystocia, in which the baby's shoulders won't
move past the mother's bony pelvis during delivery, occurs
in about 5 percent of births. Of these, up to a quarter of
deliveries may result in an injury to the baby's brachial
plexus, the nerves that control movement and sensation in
the arm. As many as 10 percent of infants may sustain some
An obstetrician can perform one of several maneuvers
to manipulate the position of either the mother or the baby
when shoulder dystocia occurs. The Johns Hopkins
researchers found that turning the baby so its spine faces
the mother's belly (a technique known as anterior Rubin's
maneuver) requires less force than either turning the baby
so its spine faces the mother's spine, or moving the
mother's legs back to try to reduce the force of the baby's
shoulders against the mother's pelvis.
These results were reported in the Jan. 4 issue of the
American Journal of Obstetrics and Gynecology.
"Every obstetrician is likely to face this
circumstance at some point in his or her career, and the
longer the baby remains stuck, the higher the risk that the
baby will suffocate," said Edith D. Gurewitsch, lead author
of the study and an assistant professor of
obstetrics. "While further studies are necessary before
we can make definitive recommendations on the use of one
procedure over another, our initial lab results demonstrate
that we can measure what is happening to the baby during
birth, and that we can alter our techniques to create a
safer environment for delivery--a goal shared by every
For the study, Gurewitsch performed 30 mock deliveries
using a complex birthing device designed by Johns Hopkins
faculty, staff and students to simulate shoulder dystocia.
It consists of several parts: a maternal model with a
three-dimensional bony pelvis, a fetal model, a
force-sensing glove and a computer-based data acquisition
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 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
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 bone, whereas raising the
mother's legs produced only 1 centimeter of extra space.
"Since complicated deliveries comprise a small
percentage of vaginal births, clinicians in training often
do not have adequate exposure to these types of
deliveries," said Robert H. Allen, senior author of the
study and a senior engineering lecturer at Johns Hopkins.
"Our device provides an opportunity to simulate birth
complications and allow clinicians to practice resolving
them. Using this birthing simulator as a research tool, we
may be able to glean new insights into complicated births
and develop new ways to resolve them."
The device won top prize in a student design
competition held in September during the international
meeting of the Institute of Electrical and Electronics
Engineers' Engineering in Medicine and Biology Society in
San Francisco. The inventors, including Gurewitsch, Allen
and Paul Gilka, manager of the laboratory that housed the
work, have filed a provisional patent on the simulator.
In continuing work with the laboratory model,
Gurewitsch and Allen plan to have other doctors train on
the simulator to develop a better sense of how much force
they apply to babies during delivery.
The current study was funded by grants from the
National Center for Injury Prevention and Control, a branch
of the federal Centers for Disease Control and
Study co-authors were Esther J. Kim, Jason H. Yang,
Katherine E. Outland and Mary K. McDonald.
To watch a video of the student design team working on
an earlier prototype, go to