Transcript Assisted Birth - Southeastern Louisiana University

ASSISTED BIRTH
DIFFERENCES BETWEEN HUMAN AND
NON-HUMAN PRIMATE BIRTHS
Wenda Trevathan (1987) proposed three primary differences between
human & non-human primate births.
Trevathan’s conclusions are based upon observations of over 250
human births (out of the hospital) and a limited set of observations of
non-human primate births (in and out of captivity).
DIFFERENCES BETWEEN PRIMATE
BIRTHS
Non-Human Primate
Human Primate
1.) Birth tends to be nonrotational
2.) Emerge from birth
canal facing same
direction as mother
3.) Typically occur in
isolation
1.) Almost universally
rotate
2.) Emerge from birth
canal facing away from
mother
3.) Often occur with
assistance
The Root of the Downward (Birth)
Rotation
•
Quadrupedal
•
Bipedal
•
Upright walkers
•
“Knuckle-walkers”
• About 5 million years ago, evolutionary selection
for bipedalism began.
•
Skeletal changes in:
•
•
Feet, spine, legs, knees, ribcage…
PELVIS
•
Obstetrical dilemma
Evolution of Human Primate Brain Size
Bipedalism & Big Brain
■ The changes in the skeletal structure of
the pelvis due to the evolution of
bipedalism also changed the shape of
the birth canal over time. (Weaver &
Hublin 2009)
• With the added increases in brain size, “the
net effect is that human neonatal head size
closely matches maternal pelvic
dimensions, unlike in our closest living
relatives, the great apes, whose pelvic
dimensions are larger than neonatal head
sizes.” (Franciscus 2009)
FETAL ROTATION
■ Fetal rotation
– Passive movement as a result of
neonate coming into contact with
bony portions of the pelvis and
highly resistant muscles of the
pelvic floor
EMERGING FROM THE BIRTH CANAL
Non-Human Primates
■ Occiput posterior (OP)
– Infants emerge from birth canal facing the
same direction as the mother
–
The facial presentation of non-human
primates allows the mother to easily
access her infant once it emerges or
during the birthing process.
Human Primates
■ Occiput anterior (OA)
– Infants emerge from birth canal facing
away from the mother
■ If mother encounters some complication
during birth, bending over could be
detrimental to her and the infant.
Motor Skills
■ Infants often have the motor ability to use their
hands to get out of the birth canal
■ Retained motor skills over course of evolution to grip fur
– Possible relationship between brain growth of infant at
birth
■
Non-human primates: 50%
■
Human primates: 29%
Complications During Human Birth
■ Shoulder dystocia - shoulders get stuck in the birth canal
– Largest width of infant shoulders is perpendicular to the
width of the head
■ Nuchal cord – umbilical cord wraps around infant’s neck
– Occurs in 23-33% of births
■ Mother unable to remove fluids preventing infant from
breathing after emerging
■ Occipital posterior emergence
– Occurs in about 1% of births
ASSISTED BIRTH: UNIQUELY HUMAN?
■ Assisted birth for human primates is
largely universal
■ Assisted birth in non-human
primates does occur:
–
Obligate midwifery
–
296 cultures noted to have some
mention of assistance during birth
–
Pair bonds in New World monkeys
–
Orangutans
24 of these report some form or custom of
unattended birth
–
Protecting mother from infanticide
■
■ Extends beyond the birthing process
–
Example: zuo yuezi (Raven et al., 2007)
Major difference in assisted birth in human primates versus non-human primates:
Human primates more directly involved in assistance.
CONCLUSION
“Selection for bipedalism set hominids
on a trajectory toward the elaboration of
cultural systems of authoritative
knowledge about how childbirth could
best be accomplished.” (Trevathan 1996)