Physiologic Basis of Fetal Heart Monitoring

Maternal Fetal Circulation

     Oxygen delivery to the fetus is via the uterine arteries to the uterus, from the uterus through the placenta, and from the placenta to the fetus via the unbilical vein.  Within the placenta, oxygen and nutrient delivery and carbon dioxide and waste removal are facilitated by the intervillous space between placental and uterine tisssue.  The umbilical vein delivers nutrient and oxygen rich blood to the fetus while two umbilical arteries bring carbon dioxide and waste products to the placenta for removal by the uteine veins.

    With each uterine contraction uterine and placental blood flow are reduced (like a sponge being squeezed) resulting in a temporary decrease in placental oxygen exchange.  When the uterus relaxes, uterine perfusion normalizes and placental oxygen exchange resumes.

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