Katherine D.,
There are a few problems with using the Cesarean rate for CPD as an indicator
of true cephalopelvic proportion. 1. American women are generally expected to
give birth in lithotomy position, which constricts the pelvis; as opposed to
squatting, which enlarges the pelvic outlet. 2. Women having VBAC's (Vaginal
Birth After Cesarean) usually sucessfully birth a larger baby than their "CPD"
C-section baby. Obviously there are other factors. 3. A small baby does not
lead to a less problematic birth: a large head is desirable to provide a
wedge for cervical dilitation, a small head (or malpresentation) allows the
possibility of umbilical cord prolapse or limb presentation. One of my
college professors used to offer a complicated proof that babies over 7 lbs
were easier to deliver because they adequately supported the mechanics of
labor. 4. The size of the smallest pelvic diameter is about 13 inches. Then
the infant head is compressible, the symphisis pubis is expandable in a
crunch...so there is more to CPD than size. 5. epidurals relax the pelvic
musculature, reducing the stimulus for infant rotation, these 'persistent
posterior' babies are not properly aligned with the pelvis to allow easy
birth. With many OB's limiting the second stage of labor to 2 hours, these
babies are often cut out. I could go on forever. I think we need to be
cautious about taking the "American" statistics at face value, and need to
look at the practices that lead to these CPD diagnoses.
My C-section was for "CPD"; my son was breech and 2nd stage was
limited to 1 hour. This is obviously not CPD, but physician distress and
maybe Sacro-pelvic disproportion! His little sister was born at home, same
size within 1/2 ounce and 1/2 inch; was out in 45 minutes of pushing in a
semi-squatting position. I know many moms who had 9,10 and 11 lb. babies at
home. Tom Brewer, MD, claims that well nourished moms will have the muscle
strength and tissue flexibility to birth large babies. The Brewer diet
focuses on protein (100g), fruits and veggies, and grains. I only ate 80g
protein/day during my pregnancies, I did not feel confident about birthing a
10 pounder! Mine were a manageable almost 8.
Sorry for the tirade, but the US cesarean section rate is another of
my pet peeves!
Catherine Watson Genna, IBCLC
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