The fetal circulation allows for oxygenated blood to pass from the placenta to the fetus and deoxygenated blood to return to the placenta. Three key shunts exist in the fetal circulation - the ductus venosus, ductus arteriosus, and foramen ovale - which ensure blood bypasses the lungs and allows for oxygenated blood to reach the fetus. At birth, clamping of the umbilical cord and inflation of the lungs causes structural changes, closing the shunts and transitioning circulation to the infant pattern with blood flowing to the lungs.

1. FETAL CIRCULATION

2. DEFINITION
• The circulation of oxygenated blood, de-oxygenated
blood, nutritive material etc. in the fetus is termed as
fetal circulation
• The fetal circulation is the circulatory system of a
human fetus, often encompassing the entire
fetoplacental circulation which includes the umbilical
cord and the blood vessels within the placenta that
carry fetal blood.

3. PATHWAY
Umbilical Vein
Placenta
Umbilical Arteries
Foramen Ovale
Right Atrium
InferiorVenacava
Ductus Venosus
Liver
Archof Aoarta
Right Lung
Ductus Arteriosus
Left Atrium
Left Ventricle
RightVentricle
Portal Vein

4. UMBILICAL
CORD
⚫2umbilical arteries:
return non-oxygenated blood, fecal waste,
CO2 to placenta
⚫1umbilical vein:
brings oxygenated blood and nutrients to the
fetus

5. Three shunts are present in fetal life:
1. Ductus venosus: connects the umbilical vein to the
inferior vena cava
2. Ductus arteriosus: connects the main pulmonary artery to
the aorta
3. Foramen ovale: anatomic opening between the right and
left atrium.

6. PATHWAY
Oxygenated blood from the placenta
through umbilical vein
fetus
liver
Receives deoxygenated blood from the portal vein
through ductus venosus
Inferior vena cava
Right atrium of heart
through foramen ovale
Left atrium of the heart
Left ventricle of the heart

7. During ventricular systole
Left ventricular blood
pumped
Ascending aorta and
distributed by their branches
to the heart,
head,neck,brain,arms.
Right ventricular blood
with < o2 content
is discharged
Pulmonary arteries
Ductus arteriosus
Descending aorta
Hypogastric arteries
Umbilical arteries
Placenta

8. During fetal life 350ml/ min
Cardiac Output
Heart Rate
Following birth 500ml/min
120-140per min

9. AT BIRTH
⚫Clamping the cord shuts down low-pressure
system
⚫Increased atmospheric pressure(increased
systemicvascular resistance) causes lungs to
inflatewith oxygen
⚫Lungs now becomea low-pressure system

10. Changes in the fetal circulation after birth
⚫ Umbilical arteries → Umbilical ligaments
⚫ Umbilical vein → Ligamentum teres
Shunt Functional
closure
Anatomical
closure
Remnant
Ductus
arteriosus
10 – 96 hrs
after birth
2 – 3 wks
after birth
Ligamentum
arteriosum
Formamen
ovale
Within several
mins after birth
One year
after birth
Fossa ovalis
Ductus
venosus
Within several
mins after birth
3 – 7 days
after birth
Ligamentum
venosum

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