FETAL CIRCULATION

1.  By the third month of development, all major blood vessels are present and
functioning.
 Fetus have blood flow to & from placenta.
 Resistance to blood flow is high in lungs
DEFINITION
‘The fetal circulation is the circulatory system of a human fetus, often
encompassing the entire fetoplcental circulation which includes the umbilical cord
and the blood vessels within the placenta that carry fetal blood.’
CHARACTERISTICS
• Placenta is the source of oxygen for the fetus
• Fetus lung received less than 1 percent of blood volume
• No gas exchange occurs in lungs
• Right atrium of heart have highest concentration of oxygenated blood
• Presence of Unique structures

2. Cardiac output- during fetal life 350 ml per kg per minute
Following birth 500 ml per minute
Heart rate= 12.-140 per minute

3. Flow Chart of Fetal Circulation

4. FLOW OF CIRCULATION
• Hepatic
▫ One Umbilical vein carries 85% of oxygenated blood from placenta to
fetal side
▫ It divides into two branch, 1 to liver & another via Ductus Venosus to
inferior Vena Cava
▫ Only 25% of Blood enters hepatic circulation rest bypass into inferior
vena cava
▫ Umbilical blood flow is 180 ml/mt /kg of estimated fetal weight.
• Cardiac

5. ▫ Blood receives from Superior & Inferior Vena Cava into Rt. Atrium
pass through the Foramen Ovale to Lt. Atrium (More than 1/3rd
of total
blood received)
▫ Some blood passes from Rt. Atrium to Rt. Ventricle & from there to
pulmonary artery
▫ Blood of Lt. Atrium enters into Lt. Ventricle & from there to Aorta
(Oxygenated blood)
• Pulmonary
▫ Blood of pulmonary artery by pass the lungs & enters into Descending
aorta via Ductus Arteriosus (De-oxygenated blood)
▫ Small amount of blood reaches lungs for development & returns to Lt.
Atrium via Pulmonary Vein (No gas exchange takes place)
▫ Pulmonary blood flow is estimated to be 75 ml/kg of fetal weight
• Systemic
▫ Blood receives in aorta goes to Carotid artery & Head (maximum
oxygenated blood)
▫ Descending aorta have mixed blood to supply the lower half of the body
▫ Umbilical artery, arising from Hypo gastric artery, branch of internal
iliac artery carries waste & deoxygenated blood back to placenta
WHAT HAPPENS AT BIRTH?
The change from fetal to postnatal circulation happens very quickly.
Changes are initiated by baby’s first breath.

6. CHANGESDURINGNEONATALPERIOD
• Cessation of umbilical blood flow
• No flow in Ductus Venosus
• Fall in pressure in RA
• Closure of foramen Ovale
• Intake of first breath
• Inflation of lung
• Fall in pulmonary vascular resistance & release of Bradykinin
• Constriction of Ductus Arteriosus

7.  Nutritional – Breast feeding
 Elimination – Kidney & GI system
 Temperature regulation
 Development of communication
FETAL VS INFANT CIRCULATION
FETAL INFANT
 Low pressure system  High pressure system
 Right to left shunting  Left to right shunting
 Lungs non-functional  Lungs functional
 Increased pulmonary resistance  Decreased pulmonary
resistance
 Decreased systemic resistance  Increased systemic resistance