This document summarizes fetal and neonatal circulation. In the fetal circulation, oxygen-rich blood from the placenta travels to the fetus through the umbilical vein and ductus venosus, bypassing the lungs through fetal shunts. At birth, closure of the ductus venosus, foramen ovale, and ductus arteriosus occurs as the lungs become functional, establishing the neonatal circulation and excluding the placenta. Some fetal vessels like the ductus arteriosus and umbilical vessels form non-functional ligaments over time after birth.

1. FETAL AND NEONATAL
CIRCULATION
DR KELECHI DURUH
DEPARTMENT OF HUMAN ANATOMY
FBMS COLLEGE OF MEDICINE
UNEC
27/7/23
BY

2. OUTLINE
• INTRODUCTION
• FETAL CIRCULATION
• TRANSITIONAL CHANGES/TRANSITIONAL
NEONATAL CIRCULATION
• DERIVATIVES FROM THE TRANSITIONAL
CHANGES
• CLINICAL CORRELATES
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3. INTRODUCTION
• In fetal circulation, the placenta supplies oxygen,
nutrition and aids in detoxification.
• The lungs are non-functional
• Shunts exist bypassing the lungs and liver
• Though the partial Oxygen pressure is relatively
low, tissues are adequately supplied
• Fetal circulatory system provides prenatal and
perinatal needs and allows for modification at
birth
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4. INTRODUCTION contd.
• Modifications establish neonetal circulatory
pattern
• In neonatal circulation, the lungs are aerated
• The severance of placenta from the fetus has
consequential changes
• Some circulatory components undergo functional
and anatomical changes
• Changes bring about directional and dynamic
alterations in blood flow
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5. FETAL AND NEONATAL CIRCULATIONS
FETAL CIRCULATION
NEONATAL CIRCULATION
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6. FETAL CIRCULATION
• Oxygenated, nutrient rich blood from placenta
passes through the umbilical vein
• At the area of the liver, 50% pass through the
ductus venosus(DV) into the IVC
• The other 50% pass through the portal sinus , the
portal vein, liver sinusoids, hepatic veins into the
IVC
• A sphincter in the DV regulates blood flow
• Contraction of sphincter reduces flow through
the DV increasing flow through liver sinusoids
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7. FETAL CIRCULATION contd
• The IVC drains the DV, hepatic veins and the
abdominal vein
• After a short course the IVC, empties into the
right atrium
• Most blood arriving right atrium from IVC are
directed through the foramen ovale into the left
atrium
• In the left atrium ,it mixes with a small quantity
of poorly oxygenated blood returning from the
pulmonary veins
• Left atrium empties into the left ventricle
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8. FETAL CIRCULATION contd.
FORAMEN OVALE
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9. FETAL CIRCULATION contd
• Left ventricle transmits blood through the
ascending aorta , the arch, the descending aorta,
to the arteries of the trunk and lower body
• The ascending aorta supplies the heart
• The arch supplies the head ,neck and upper limbs
• The residual volume of blood in the right atrium
mixes with poorly oxygenated blood from SVC
and coronary sinus and enters the right ventricle
• The right ventricle ejects blood through the
pulmonary trunk
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10. FETAL CIRCULATION contd
• Pulmonary vascular resistance is higher than
that of the systemic
• 90% of pulmonary trunk blood pass through
the ductus arteriosus(DA) into the descending
aorta
• 10% goes to nourish the lungs
• DA protects the lungs from circulatory
overload also aids the right ventricle in
adjusting to postnatal functioning
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11. FETAL CIRCULATION contd
• 65% of blood in the descending aorta passes
into the umbilical arteries into the placenta
• 35% nourishes the viscera and inferior part of
the body then returns to the heart through
IVC and SVC
• 90% of left ventricular ejection nourishes the
head, neck and upper limb
• 10% pass down to the descending aorta
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12. TRANSITIONAL NEONATAL
CIRCULATION
• Change from fetal to neonatal circulation is not
sudden occurrence
• Some occur with first breath others over hours or
days
• The closure of fetal vessels and oval foramen is
initially a functional change then anatomical
• At cessation of placental flow, changes occur to
exclude placenta in the circulation
• Shunt points are shut down
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13. TRANSITIONAL NEONATAL
CIRCULATION
• The foramen ovale, DA, DV and umbilical vessels
become needless
• DV sphincter constricts , diverting all blood to
portal vein
• Pressure in IVC and right atrium consequently
reduce
• Lung expansion and aeration causes decrease in
pulmonary vascular resistance and increase in
pulmonary flow
• Stretching of the lungs causes thinning of
pulmonary artery walls
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14. TRANSITIONAL NEONATAL
CIRCULATION
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15. TRANSITIONAL NEONATAL
CIRCULATION
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16. TRANSITIONAL NEONATAL
CIRCULATION contd.
• Increased pulmonary flow and cessation of
umbilical flow reduces pressure in the right
heart
• Increased pulmonary venous return builds left
atrial pressure
• Higher pressure in the left atrium relative to
right functionally closes the foramen ovale
• DA constricts at birth
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17. TRANSITIONAL NEONATAL
CIRCULATION contd.
• Small volume flow from descending aorta into
pulmonary trunk may linger for about 72hrs
• By 96hrs 100% of DA should be functionally
closed
• Oxygen is the main enhancing factor
• Closure is mediated by prostaglandin E2 and
bradykinin
• Factors that may impede normal closure
include prematurity, hypoxia etc
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18. TRANSITIONAL NEONATAL
CIRCULATION contd.
• DA constricts when PaO2 of blood in the aorta
approximates 50mmHg
• During fetal life ,patency of DA is maintained
by low oxygen and some endogenous
prostaglandins
• Umbilical arteries constricts at birth
• Blood flow in the vein continues for 1min or
more prior to tying of cord
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19. DERIVATIVES OF FETAL VASCULAR
STRUCTURES
• Certain fetal vessels and structures are
undesired in extrauterine circulation
• Within a period of time these fetal vessels
form nonfunctional ligaments
• The umbilical vein remains patent for
considerable time
• The intraabdominal part eventually becomes
the round ligament
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20. 19

21. DERIVATIVES OF FETAL VASCULAR
STRUCTURES contd.
UMBILICAL VEIN, DUCTUS VENOSUS 20

22. DERIVATIVES OF FETAL VASCULAR
STRUCTURES contd.
• DV becomes ligamentum venosum
• Distal part of umbilical arteries become the
medial umbilical ligament
• The proximal part persist as the superior
vesical arteries
• Foramen ovale closes functionally at birth
then anatomically by 3rd month
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23. DERIVATIVES OF FETAL VASCULAR
STRUCTURES contd.
• The septum primum forms the floor of the
oval fossa
• The inferior edge of the septum secundum
forms the rounded fold
• DA closes functionally within first four days of
birth
• Anatomical closure and formation of
ligamentum arteriosum occurs at 12th
postnatal week
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24. CLINICAL CORRELATES
• Patent ductus arteriosus
• Coartation of the aorta
• Double IVC, non formation of IVC
• Patent foramen ovale
• Pulmonary stenosis
• Double arch of the aorta
• Abnormal origin rt.subclavian
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25. CLINICAL CORRELATES
PATENT DUCTUS ARTERIOSUS 24

26. CLINICAL CORRELATES
PRE AND POST-DUCTAL COARTATIONS OF THE AORTA
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27. CLINICAL CORRELATES
PATENT FORAMEN OVALE
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28. GOD BLESS YOU
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