The fetal circulation differs significantly from adult circulation. During development, the placenta provides oxygen to the fetus and the lungs receive very little blood flow. The fetal circulation includes unique structures that allow blood to bypass the lungs, such as the ductus venosus and foramen ovale. At birth, breathing causes changes like closure of the ductus venosus and foramen ovale as well as a drop in pulmonary resistance, transitioning the circulation to its postnatal state where the lungs are the primary site of gas exchange.

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