By-
BARKHA DEVI
LECTURER
SMCON
FETAL CIRCULATION
INTRODUCTION
• In the fully developed human, the heart serves
two main purposes.
• The right heart pumps blood to the lungs for
oxygenation and the left heart pumps oxygenated
blood to rest of the body.
• In the embryo and fetus, the lungs do not
oxygenate the blood.
• Fetal circulation is consequently quite different
than that of a breathing baby or adult.
• When a baby is born and takes its first breathes,
the ducts close and blood is rerouted to the lungs.
Definition
The fetal circulation is the
circulatory system of a
human fetus, often
encompassing the entire
fetoplacental circulation
that also includes the
umbilical cord and the
blood vessels within the
placenta that carry fetal
blood.
Fetal Circulation
Foetal circulation consequently differs from the
adult one predominantly due to the presence of
3 major vascular shunts:
• Ductus venosus: between the umbilical vein and IVC
• Foramen ovale: between the right and left atrium
• Ductus arteriosus: between the pulmonary artery and
descending aorta
The main function of these shunts is to redirect oxygenated blood away from the lungs,
liver and kidney (whose functions are performed by the placenta).
Umbilical Circulation
• Pair of umbilical arteries
carry deoxygenated
blood & wastes to
placenta.
• Umbilical vein carries
oxygenated blood and
nutrients from the
placenta.
The Placenta
• Facilitates gas and nutrient
exchange between
maternal and fetal blood.
• The blood itself does not
mix.
Placental role
The core concept behind fetal circulation is that fetal
hemoglobin has a higher affinity for oxygen than does
adult hemoglobin, which allows a diffusion of oxygen
from the mother's circulatory system to the fetus.
The circulatory system of the mother is not directly
connected to that of the fetus, so the placenta
functions as the respiratory center for the fetus as well
as a site of filtration for plasma nutrients and wastes.
Image depicts fetal circulation. Note the areas of oxygenated blood
(red) and deoxygenated blood (blue) mixing (purple) through fetal
Fetal Circulation
• By the third month of
development, all major
blood vessels are present
and functioning.
• Fetus must have blood flow
to placenta.
• Resistance to blood flow is
high in lungs.
Difference between Adult and Fetal Circulation
Criteria Adult Circulation Fetal Circulation
Artery Carries oxygenated Carries Non-oxygenated blood away
blood away from from the fetal heart
the heart
Veins Carries non- Carries oxygenated blood back to the
oxygenated blood heart
towards the heart
Exchange Takes places in the Takes place in the placenta
of Gases lungs
Pressure Increase pressure Increase pressure on the right side of
on the left side of the heart
the heart
Fetal Circulation Sequence
Exchange of gases occurs
in the placenta.
Oxygenated blood is
carried by the umbilical
vein towards the fetal
heart.
The ductus venosus directs part of the blood
flow from the umbilical vein away from the
fetal liver (filtration of the blood by the liver is
unnecessary during the fetal life) and directly
to the inferior vena cava.
Blood from the ductus venosus enters
to the inferior vena cava. Increase
levels of oxygenated blood flows
into the right atrium.
In adults, the increase
pressure of the right atrium
causes the tricuspid valve
to open thus, draining the
blood into the right
ventricle. However, in fetal
circulation most of the
blood in the right atrium is
directed by the foramen
ovale (opening between the
two atria) to the left atrium.
The portion of the blood that drained into the
right ventricle passes to the pulmonary artery.
As blood enters the pulmonary artery
(carries blood to the lungs), an
opening called ductus arteriosus
connects the pulmonary artery and
the descending aorta. Hence, most
of the blood will bypass the non-
functioning fetal lungs and will be
distributed to the different parts of
the body. A small portion of the
oxygenated blood that enters the
lungs remains there for fetal lung
maturity.
The umbilical arteries then carry the non-
oxygenated blood away from the heart to
the placenta for oxygenation.
Flow Chart of Fetal Circulation
Why is the pulmonary circulation reduced in the human
fetus?
Pulmonary circulation is reduced in the human fetus
because the baby gets its oxygen from its mother and
does not breath on its own.
FETAL CIRCULATION VIDEO
fetal heart circulation 360p - YouTube.flv
Postnatal changes in circulation
What happens at birth?
• The change from fetal to postnatal circulation happens
very quickly.
• Changes are initiated by baby’s first breath.
Post natal changes
• Gas exchange function is transferred from
placenta to the lungs.
• Separation of systemic and pulmonary
circulations
• Increased metabolism to maintain body
temperature and hence increased cardiac output.
FETAL CIRCULATION VIII: Conversion to post-natal*
Closure of Foramen ovale
Forces venous blood (now all deoxygenated) into
the right ventricle for expulsion to the lungs
Closure of DUCTUS VENOSUS
Stops use of umbilical HEART Pulmonary
vessels, & converts all
vena cava blood to
Vena cava Right
ATRIUM
OLef t veins
LUNGS
deoxygenated ATRIUM
IVC
Right
VENTRICLE
SYSTEMIC Left Pulmonary
VENTRICLE arteries
CAPILLARIES
Closure of
Umbilical
arteries
Stops use of Aorta Closure of
umbilical vessels Ductus arteriosus
means that blood expelled from the
right ventricle has to go to the lungs
Foramen ovale Closes shortly after birth,
fuses completely in first
year.
Ductus arteriousus Closes soon after birth,
becomes ligamentum
arteriousum in about 3
months.
Ductus venosus Ligamentum venosum
Umbilical arteries Medial umbilical ligaments
Umbilical vein Ligamentum teres
Problem with persistence
of fetal circulation
• Patent (open) ductus arteriosus and patent foramen ovale
each characterize about 8% of congenital heart defects.
• Both cause a mixing of oxygen-rich and oxygen-poor
blood; blood reaching tissues not fully oxygenated. Can
cause cyanosis
• Surgical correction now available, ideally completed
around age two.
• Many of these defects go undetected until child is at least
school age.
ADULT DERIVATIVES OF FETAL VASCULAR
STRUCTURES
S.No FETAL STRUCTURE ADULT STRUCTURE
1. FORAMEN OVALE FOSSA OVALIS
2. UMBILICAL VEIN LIGAMENTUM TERES
3. DUCTUS VENOSUS LIGAMENTUM VENOSUM
4. DUCTUS ARTERIOSUM LIGAMENTUM ARTERIOSUM
5. UMBILICAL ARTERY AND MEDIAL UMBILICAL ARTERY
ABDOMINAL LIGAMENT AND SUPERIOR VESICULAR
ARTERY
?
BIBLIOGRAPHY
Daftary,N.Shirish. (2002).Manual Of Obstetrics
2 nd Edition. New Delhi: Elsevier Publisher Page No:39-45
Dutta,D.C.(2004).Textbook Of Obstetric
6thEdition.Calcutta :New Central Book Agency Page No:41-
45
Gary, Cunningham and Leveno,Kanneth.(2004).
Williams Textbook Of Obstetrics
22th Edition.Mc Graw Hill:Lippincott Williams & Wilkins Page
No:91-104
•Singh,Inderbir.(1996).Human Embryology, 6th Edition.New
Delhi:Macmillan India Limited Page No.257-259
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