Fetal hemoglobin has a HIGH affinity for oxygen because maternal oxygen is around 16% in the blood stream, therefore the need for higher affinity. This is why fetal hematocrits are higher than maternal or adult, and why infant no longer needs the norm of 55-65% hematocrit to support cellular function. Normal adult is 35-42% (American values) (I am quoting from memory not researching, don't have time now).
-----Original Message-----
From: Lactation Information and Discussion [mailto:[log in to unmask]] On Behalf Of Diane Wiessinger
Sent: Thursday, January 15, 2009 1:59 PM
Subject: fetal hemoglobin and oxygen
I was sent this e-mail note from an IBCLC friend studying for the exam. Everything *I* found on-line disagreed with R&A. Does anyone know for sure?
Diane Wiessinger, MS, IBCLC, LLL Leader, Ithaca, NY USA www.normalfed.com
Question (from Study Guide for BF & Human Lactation by Riordan & Auerbach) :
Fetal hemoglobin
a. picks up oxygen poorly.
b. has a high affinity for oxygen
(c & d were quickly eliminated)
The correct answer was given as "a" with this explanation from the book:
Riordan & Auerbach's BF & Human Lactation...
Fetal hemoglobin is well adapted to assisting the fetus in the low-oxygen environment of the uterus. It has a low affinity for oxygen; therefore, it picks up oxygen less well than does adult hemoglobin (which has more need for it). However, it also is better able to release the oxygen to peripheral tissue, thus enabling the fetus to live and grow in a relatively low-oxygen environment.
It previously explained that fetal hemoglobin takes up oxygen poorly, so more hemoglobin is needed. The normal, full-term baby is born with a relatively high level of red blood cells containing a high level of fetal hemoglobin.
One of my study-mates had checked on line and found this conflicting statement re: fetal hemoglobin and its affinity for oxygen as compared to the adult hemoglobin...
http://en.wikipedia.org/wiki/Fetal_hemoglobin
Fetal hemoglobin, or Foetal haemoglobin in British English, (also hemoglobin F or HbF) is the main oxygen transport protein in the fetus during the last seven months of development in the uterus and in the newborn until roughly 6 months old. Functionally, fetal hemoglobin differs most from adult hemoglobin in that it is able to bind oxygen with greater affinity than the adult form, giving the developing fetus better access to oxygen from the mother's bloodstream.
What's your take on this...does fetal hemoglobin have a low or high affinity for oxygen and why?
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