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Lecture 26

BIOCHEM 4M03 Lecture Notes - Lecture 26: Fetal Circulation, Insulin Resistance, Catabolism

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Deborah Sloboda

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Biochem 4M03 – Lecture 26 - Maternal Undernutrition
Intrauterine Growth Restriction (IUGR)
-Low birth weight and IUGR are not the same thing
-Born early so its small
-Failure of fetal growth
-Can be caused by:
Poor nutrition (malnutrition)
Disease (renal, cardio)
Drugs (smoking, etc.)
Poor blood flow (reduction in blood flow)
Multiple gestation (>1 baby)
In twins, often one twin is larger
Chromosomal anomalies
-Blood flow one of mediators of fetal growth
What causes low birth weight babies?
-Premature baby in a previous pregnancy
-Pregnant with twins, triplets or more
oWhy does more than one baby = LBW  Maternal Constraint!
-Abnormalities of the uterus or cervix
-Congenital defects
-Inadequate maternal weight gain
-Socioeconomic factors
oQuality of healthcare, better supplementation, micronutrients you may not be
getting in your diet, higher stress lifestyle (higher maternal cortisol), higher fat
diet (fetus growing off processed foods), knowledge base
-Placental insufficiency
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oPlacental problems can reduce flow of blood and nutrients to the fetus, limiting
oInsufficient implantation, insufficient growth of vessels, all contribute to changes
in fetal growth
oIn some cases, a baby may need to be delivered early to prevent serious
complications in mother and baby
Placental transport and abnormal fetal growth
-Placental insufficiency and abnormal fetal growth
-Intrauterine growth restriction (IUGR) occurs through:
oUteroplacental blood flow reduction (reduction in maternal cardiovascular
oAbnormal villi development/structure/function
Villus: Trees that branch in, makes direct contact between fetal tissue and
maternal blood vessel, important to have because if not enough might not
reach blood vessels
oPoor oxygenation (hypoxia) – could be due to smoking
oImpaired nutrient transport
Flow rates – Maternal (uterine) blood flow
-Human pregnancy
oUterine flow increases from 60ml/min to 700-800ml/min throughout pregnancy
-Flow rate to uterus increases from beginning to end
oMaternal blood flow to uterus
-Blood volume increases significantly
-Example below is what happens when blood flow is restricted
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oMeasured resistance in blood vessels of placenta in sheep and looked at
whether or not restriction was associated with intrauterine growth restriction
oFound it was directly associated – increase in resistance = increased potential in
intrauterine growth restriction (due to reduction in blood flow)
-Placental vascular resistance in IUGR sheep fetuses  decrease in blood flow
Surface area is reduced in human IUGR in conjunction with changes in villi development
and function
-Growth restricted versus control, looked at placenta
-Reduction in trophoblast (cell derived from fetus) volume, villus surface area and
capillary surface
What happens if blood flow is restricted (vascular resistance?)
-Increased exchange barrier thickness in FGR – reduced oxygen diffusional capacity
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