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Fetal Circulation and
Newborn Transition to Life
Melissah Burnett & Jacqui McGregor
La Trobe University, Melbourne.
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• Some cardiac abnormalities are considered
“duct-dependent”; these can be cyanotic or
acyanotic
• Duct-dependent defects can be related to
pulmonary flow (for example pulmonary
stenosis or pulmonary atresia); or related to
systemic flow (for example hyperplastic left
heart or transposition of the greater arteries)
• If there is a definite or suspected diagnosis of a
cardiac abnormality, that is duct dependent, a
prostaglandin infusion is the treatment of
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choice (a synthetic version of the hormone
that
Objectives
• To have an understanding of the anatomy and
physiology of fetal circulation
• To identify the 3 fetal shunts
• To have an understanding of newborn transition
and conversion of fetal to neonatal circulation
• Identify impediments to this transition
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Survival Tasks
The newborn, must make five major
adjustments at birth.
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1) World of air
2) Circulation
3) Wastes
4) Body temperature
5) Response to infection
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Adult Heart
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Review pulmonary & systemic circulations and
anatomy of the heart.
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Anatomical Structures of Fetal Circulation
Includes:
• Placenta
• Umbilical Vein (X1)
• Ductus Venosus
• Foramen Ovale
• Ductus Arteriosus
• Umbilical Arteries (X2)
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Placental Transport
• The main functions of the placenta include:
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Gas exchange
Nutrients
Disposal of waste products
Hormones
• Other things can cross placenta
– maternal antibodies
– drugs
– infectious agents
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Placenta
• Facilitates gas and nutrient
exchange between maternal
and fetal blood.
• These substances diffuse
between maternal and fetal
blood through the placental
membrane.
• The blood itself does not mix.
• The placenta is a low
resistance component of the
fetal circulation.
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The Placenta
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Umbilical Circulation
• An umbilical vein
carries oxygenated
blood and nutrients
from the placenta to
the fetus.
• A pair of umbilical
arteries carry
deoxygenated blood
& wastes from the
fetus to placenta.
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Umbilical Vein
• Transports O2 rich
blood & nutrients
• Enters ductus
venosus
• 80% saturated with
O2
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Ductus Venosus
• Approximately 45% of blood
from the umbilical vein enters
the portal circulation allowing
the liver to process nutrients.
• Approximately 55% of the
blood passes thru the Ductus
Venosus, a shunt which
bypasses the liver.
• The ductus venosus travels a
short distance and joins the
Inferior Vena Cava.
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Umbilical Vein
• Blood continues to travel up the Inferior
Vena Cava
• Empties into the Right Atrium of the
heart
• A large portion of the blood is shunted
into the Left Atrium through the
Foramen Ovale
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Fetal Circulation Differences
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Placenta
Umbilical Vein
Liver
Ductus Venosus
Inferior Vena Cava
Right Atrium
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Foramen Ovale
• Blood is shunted directly
into the left atrium
through an opening
called the foramen
ovale.
Foramen
Ovale
• R ►L shunt
• There is a valve with two
flaps that prevents backflow.
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Blood Flow thru Heart
• Blood continues the 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
via the Superior Vena Cava
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Right Atrium
Foramen Ovale
Left Atrium
Left Ventricle
Aorta
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Blood flow thru Heart
• The remaining of the fetal blood in the Right
Atrium, including a large proportion of the
deoxygenated blood returning from the
Superior Vena Cava passes into the Right
Ventricle and out through the Pulmonary
Trunk.
• The blood continues along the Pulmonary
Artery the majority is shunted away from the
lungs thru the Ductus Arterious into the
Aorta Arch a small amount goes to the
maturing lungs.
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Fetal Circulation Routes - through the Heart
Right Atrium
Right Ventricle
Pulmonary Artery
Ductus Arteriosus
Aorta
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Aorta
Common Iliacs
Internal Iliacs
Umbilical Arteries
Placenta
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Pulmonary Resistance
• ▲Pulmonary
Vascular resistance
due to partially
collapsed alveoli
• ▼blood flow to lungs
• Relative hypoxia
• Vasoconstriction
Pulmonary
Vascular
Constriction
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Ductus Arteriosus
• A vascular connection
between the Pulmonary
Artery and the Aorta.
• It allows blood to bypass
non-functioning lungs
and return to the
placenta via the
Descending Aorta and
Umbilical Arteries
• Returns blood to placenta
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Ductus Arteriosus
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Blood Flow
• Fluids always follow the path of
least resistance.
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Umbilical Arteries
• Returns
deoxygenated blood
from Descending
Aorta to placenta
• Re-oxygenated in the
placenta
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Fetal vs. Neonatal Circulation
Fetal
• Low pressure system
• Lungs non-functional
• Right to left shunting
in the heart
• High pulmonary
resistance
• Low systemic
resistance
Neonate
• High pressure system
• Lungs functional
• Left to right blood
flow in the heart
• Low pulmonary
resistance
• High systemic
resistance
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Intra-Uterine Circulation
• High pressure in right atrium
and low pressure in left
atrium
• RL via foramen ovale
• Fetal pulmonary vascular
resistance high
• RL via ductus arteriosus
• Fetal systemic vascular
resistance low
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Conversion:
Fetal to Neonatal Circulation
• At birth the first breaths are the catalyst for
the transition to neonatal circulation
– Lungs inflate with oxygen with an increased
atmospheric pressure
– Lungs now become a low-pressure system as
pulmonary vessels dilate with rise in oxygen level
– Alveolar fluid is displaced
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Transition
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Decreased Pulmonary Resistance
• Pulmonary vessels vasodilate
• Fall in PVR
• Increased PBF
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Closure of the Ductus Arteriousus
• Highly oxygenated arterial blood in the Ductus
Arteriosus causes it constrict.
• Cessation of circulating PGE2 from maternal
circulation. And increased metabolism of
circulating prostaglandins by the lungs
• Bradykinin – released on lung inflation
• Within 10-15 hours the DA constricts and will
eventually become the Ligamentum Arteriosus
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Increased Systemic Pressures
• Clamping the cord shuts down the low
pressure placental system and increases
systemic vascular resistance
• Blood is now pumped to the heart and
lungs for oxygenation rather than the
placenta
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Closure of the Foramen Ovale
• Increased blood flow of
oxygenated blood
returning from the lungs
• Increases the pressure to
the left side of the heart
forces blood against the
Septum Primum causing
the Foramen Ovale to
close and become Fossa
Ovalis
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Closure of the Ductus Venosus
• Clamping of the umbilical cord increases
systemic vascular resistance
• Ductus Venosus constricts and becomes
the Ligamentum Venosum
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Function/Structural Closure
• Functional closure of the foramen ovale
and ductus arteriosus occurs soon after
birth
• Overall anatomic changes are not
complete for weeks
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Extra-uterine Circulation
• Lungs inflate  decrease in pulmonary vascular
resistance and increase in pulmonary vascular flow
• Blood O2 levels rise  further decrease in pulmonary
vascular resistance and ductus arterious constricts
• Increased pressure in LEFT atrium and decreased
pressure in RIGHT atrium  formamen ovale closes
• Umbilical cord is clamped  ductus venosus closes 
increased systemic vascular resistance
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Conversion: Fetal to Infant Circulation
• 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
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Conversion: Fetal to Neonatal Circulation
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
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http://www.youtube.com/watch?v=T79sMq
vN3BE
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Common Defects
• Patent Ductus Arteriousus
– Prems, hypoxia, immaturity
• Patent Foramen Ovale
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Stimuli To Initiate The First Breath
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Temperature change
Light stimulation
Noise
Cold
Touch
Physical stimulation /proprioception
Respiratory and metabolic acidosis
Negative pressure in the chest cavity resulting
from the recoil of the chest after exiting the
vaginal canal
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Normal Transition
• These major changes take place within seconds
of birth:
• Fluid in the alveoli is absorbed and replaced by air
• Umbilical arteries and veins constrict with clamping
• Blood vessels in lung tissue relax increasing pulmonary
blood flow
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First breath
• PVR
SVR
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http://www.embryology.ch/anglais/pcardio/u
mstellung02.html
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When things go wrong in the
Transition
Group Work
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What may contribute to abnormal
transition and what will be the
outcome in relation closure of fetal
shunts .........
Failure to take first breath
and/or sustain adequate
breathing
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What may contribute to abnormal
transition and what will be the
outcome in relation closure of fetal
shunts .........
Excessive blood loss or poor
cardiac contractility
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What may contribute to abnormal
transition and what will be the
outcome in relation closure of fetal
shunts .........
Sustained constriction of
pulmonary arterioles
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What may contribute to abnormal
transition and what will be the
outcome in relation closure of fetal
shunts .........
Stress
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What may contribute to abnormal
transition and what will be the
outcome in relation closure of fetal
shunts .........
Prematurity
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What may contribute to abnormal
transition and what will be the
outcome in relation closure of fetal
shunts .........
Inter-uterine distress
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What may contribute to abnormal
transition and what will be the
outcome in relation closure of fetal
shunts .........
Congenital cardiac
abnormalities
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What may contribute to abnormal
transition and what will be the
outcome in relation closure of fetal
shunts .........
Pulmonary abnormalities
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Birth Asphyxia
• Failure to initiate and sustain breathing at
birth
• Cascading events
• Hypoxaemia  hypoxia  damage
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Abnormal Transition
• In response to interruption in normal
transition
• lungs fail to relax
• arterioles in bowel, kidneys, muscles and skin
CONSTRICT
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Abnormal Transition
• Blood flow is redirected to the heart, brain and adrenals
PRESERVED
• If oxygen deprivation continues:
• Myocardial function and cardiac output fall
DETERIORATE
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Abnormal Transition
Blood flow to all organs is reduced

lack of adequate organ perfusion
& tissue oxygenation

brain damage
& multisystem organ damage

DEATH
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Impediments To The Transition.
• The Five H’s
–Hypothermia
–Hypoxia
–Hypoglycaemia
–Hypotension
–Hypercarbia
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Impediments To The Transition.
• Inter-uterine distress
• Congenital cardiac abnormalities
• Pulmonary abnormalities
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What Can Go Wrong During Transition?
• Insufficient ventilation and/or airway blockage
• Excessive blood loss or poor cardiac contractility
• Sustained constriction of pulmonary arterioles
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Clinical Manifestations Associated with
Asphyxia
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Factors Influencing Organ Injury
Duration of the insult
Adaptive mechanisms of the fetus
Cause of the asphyxial process
e.g.abruption versus infection
Associated event/s- e.g.meconium
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Clinical Manifestations Associated with
Asphyxia
• CNS- may range from hyper alert to moderate
and/or severe encephalopathy  seizures
• Renal - oliguria (UO < 1 cc/kg/hr) or anuria
• Fluid retention- maybe secondary to urine
output, SIADH, rhabdomyolysis
• Cardiac dysfunction- right or left sided
ventricular dysfunction alone/combined 
hypo/hypertension
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Clinical Manifestations Associated with
Asphyxia
• Pulmonary - PPHN, haemorrhage
• Gastro-intestinal- ileus, bloody stools, NEC
• Hepatic- transaminase elevation, cholestatic
jaundice
• Metabolic/endocrine-hypoglycaemia,
hypocalcaemia hypomagnesaemia,
• Hematological-bleeding
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References
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American Academy of Pediatrics
– Textbook of Neonatal Resuscitation 4th Ed (2000)
– NRP Slide Presentation Kit
Askin,D.F. (2001) Complications in the Transition from Fetal to Neonatal Life
JOGNN Vol33(3) 318-327
Blackburn,S. (2006) Placental Fetal and Transitional Circulation Revisited. Perinatal
Neonatal Nursing Vol20 (4) 290-294
Witt C. (1997) Cardiac Embryology. Neonatal Network Vol16(1) 43-49
Merenstein, G.B & Gardner, S.L, (2002), Handbook of Neonatal Intensive Care ,
5th Ed, Mosby, St. Louis.
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www.echocharity.org.uk
http://www.nhlbi.nih.gov/health/dci/Diseases/pda/pda_heartworks.html
http://user.gru.net/clawrence/vccl/chpt1/fetcirc.HTM
http://www.cayugacc.edu/people/facultypages/greer/biol204/heart4/heart4.html
• http://www.indiana.edu/~anat550/cvanim/fetcirc/fetcirc.html
• http://www.embryology.ch/anglais/pcardio/umstellung01.html
• http://mcb.berkeley.edu/courses/mcb135e/fetal.html
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Good Websites
• http://www.indiana.edu/~anat550/cvanim/f
etcirc/fetcirc.html
• http://www.embryology.ch/anglais/pcardio/
umstellung01.html
• http://www.youtube.com/watch?v=T79s
MqvN3BE
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