1. Fetal Circulation
Dr.(Mrs.)S.Valliammal
Lecturer
College of Nursing
NIMHANS
Bangalore

2. Anatomy and Physiology
Fetal Circulation
 Umbilical cord
 2 umbilical arteries: return de-
oxygenated blood, fecal waste,
CO2 to placenta
 1umbilical vein: brings
oxygenated blood and nutrients
to the fetus

3. Special Structures in Fetal Circulation
 Placenta – Where gas exchange takes place during fetal
.life
 Umbilical Arteries – Carry deoxygenated blood from the
fetus to placenta
 Umbilical Vein – Brings oxygenated blood coming from
the placenta to the fetus
 Foramen Ovale – Connects the left and right atrium. It
pushes blood from the right atrium to the left atrium.
 Ductus Venosus - Carry oxygenated blood from umbilical
vein to inferior vena cava, bypassing fetal liver
 Ductus Arteriosus - Carry oxygenated blood from
pulmonary artery to aorta, bypassing fetal lungs.

4. Flow Chart of Fetal Circulation

6. Anatomy and Physiology
 Fetus depends on placenta to meet O2 needs while
organs continue formation
 Oxygenated blood flows from the placenta to the fetus
via the umbilical vein

7. After reaching fetus the
blood flows through the
inferior vena cava

8. Fetal Circulation
 Blood continues to travel to the inferior vena cava from
the ductus venosus
 Ductus Venosus
 Small amount of blood routed to growing liver
 Increased blood flow leads to large liver in newborns

9. Fetal Circulation
 Blood continues to travel up the inferior
vena cava
 Empties into the right atrium of the
heart
 The blood then passes to the left atrium
through the foramen ovale

10. Fetal Circulation
 Foramen ovale
 Small
opening in the septum of the heart
 Completely bypasses the non-functioning lungs
 Blood continues journey to the left ventricle
blood is then pumped into the aorta
 Blood is circulated to the upper extremities
 Blood then returns to the right atrium

11. Fetal Circulation
 From the right atrium, the blood goes to the right
ventricle then to the pulmonary arteries
 Pulmonary arteries
Small amount of blood goes to the maturing lungs
 Rest of blood is shunted away from lungs by ductous
ateriosus back to aorta

13. Fetal Circulation
 Blood travels back from aorta to the two umbilical
arteries to the placenta
 The placenta will re-supply the blood with oxygen
 Fetal circulation is a low-pressure system

14. Why more blood flow directly to the
Left atrium?
 Due to the higher pressure of the blood in the inferior vena
cava, more blood flows from it directly into the left atrium via
the foramen ovale.
 foramen ovale opens like a valve and can direct the blood
stream that comes from below directly into the left atrium.
 the diameters of the inferior and superior vena cava are
larger than that of the foramen ovale and therefore a small
portion of the blood seeps into the right ventricle via the
tricuspid valve.
 The heart is filled only with a mixed blood.

15. Fetal Circulation
 Low pressure system
 Lungs are closed
 Most oxygenated blood flows between the atria of the
heart through the foramen ovale

16. Conversion of Fetal to Infant Circulation
 At birth
 Clamping the cord shuts down low-pressure system
 Increased atmospheric pressure(increased systemic
vascular resistance) causes lungs to inflate with oxygen
 Lungs now become a low-pressure system
 Pressure from increased blood flow

17. Conversion: Fetal to Infant Circulation
 In the left side of the heart causes the foramen ovale
to close.
 More heavily oxygenated blood passing by the ductus
arteriosus causes it constrict.
 Functional closure of the foramen ovale and ductus
arteriosus occurs soon after birth.
 Overall anatomic changes are not complete for weeks
Contd….

18. What happens to these special
structures after birth?
 Umbilical arteries atrophy
 Umbilical vein becomes part of the fibrous support
ligament for the liver
 The foramen ovale, ductus arteriosus, ductus
venosus atrophy and become fibrous ligaments

19. Overview of Conversion
 Umbilical cord is clamped
 Loose placenta
 Closure of ductus venosus
 Blood is transported to liver and portal system
Contd….

20. Loss of placenta also leads to :
 First breath
 Lungs expand and fluid is expelled
 Decreased pulmonary resistance
 Increased pressure in left atrium
 Closure of foramen ovale
Contd….

21.  Loss of placenta
 Increased systemic resistance
 Pressure in right atrium decreased
 Change from right to left shunting to left to right blood
flow
 Increased O2 levels in pulmonary circulation
 Closure of the ductus arteriosus
Contd….

22. Fetal vs. Infant Circulation
 Fetal  Infant
 Low pressure system  High pressure system
 Right to left shunting  Left to right blood flow
 Lungs non-functional  Lungs functional
 Increased pulmonary  Decreased pulmonary
resistance resistance
 Decreased systemic  Increased systemic
resistance resistance

23. Conclusion
 Oxygenated blood enters the umbilical vein from the
placenta
 Enters ductus venosus
 Passes through inferior venacava
 Enters the right atrium
 Enters the foramen ovale
 Goes to the left atrium
 Passes through left ventricle
 Flows to ascending aorta to supply nourishment to the
brain and upper extremities
Contd….

24. . Enters superior vena cava
 Goes to right atrium
 Enters the right ventricle
 Enters pulmonary artery with some blood going to the
lungs to supply oxygen and nourishment
 Flows to ductus arteriosus
 Enters descending aorta ( some blood going to the
lower extremeties)
 Enters hypogastric arteries
 Goes back to the placenta
End