Fetal circulation differs significantly from adult circulation. In the fetus, oxygenated blood from the placenta travels through the umbilical vein to the ductus venosus and inferior vena cava into the right atrium. Most blood then passes through the foramen ovale into the left atrium and ventricle before being pumped through the aorta to the body. After birth, closure of the ductus venosus, ductus arteriosus, and foramen ovale, along with establishment of pulmonary circulation through breathing, complete the transition to adult circulation. Persistence of fetal circulatory structures like the patent foramen ovale or ductus arteriosus can cause clinical issues.

1. Fetal
Circulation
Dr. Komal Parmar

2. Embryonic circulation
 Figure 6.15 Extraembryonic blood vessel formation in the villi,
chorion, connecting stalk, and wall of the yolk sac in a
presomite embryo of approximately 19 days. Langman’s
th

3. Embryonic circulation
Hill, M.A. 2017 Embryology Embryonic Circulations.jpg. Retrieved November 24, 2017,
from https://embryology.med.unsw.edu.au/embryology/index.php/File:Embryonic_Circulations.jpg

4. Placental Circulation
 Organ
facilitating
gaseous and
nutrient
exchange
between the
fetal and
maternal
compartmen
t
 Fetal
Part-
Develops
from
trophoblast
and
chorionic
plate.
 Maternal
Part-
Develops
from decidua
basalis.
Begins around the 8th week of Gestation.

5. Implantation and Invasion of
Uterine Tissue

7. Growth of Placenta

12. Difference between fetal and
neonatal/adult circulation
Fetal Neonatal
Gas exchange Placenta Lungs
RV, LV
circuit
Parallel Series
Pulmonary
circulation
High
resistance
Low
reistance
Fetal heart
contractility
weak strong
Dominant
ventricle
right left

13. Course of Fetal
Circulation

14. 1. Placenta

15. Transport across placent
2 types
Uteroplacental flow
 Blood circulation, ions
and gases: 500ml/min
 Lipids
 Antibodies
 Endocrine functions:
various oestrogens, β-
endorphins,
progesterone, hCG
and human chorionic
somatomammotropin
(hCS), which is also
known as placental
lactogen (hPL)
 11beta-HSD2
 Drugs
 Microbes

16. 2. Fetoplacental Circulation

17. 2. Umbilical Vein
 Form by the convergence of
venules that drain the
splanchnopleure of the
extraembryonic allantois.
 The peripheral venules drain the
mesenchymal cores of the
chorionic villous stems and
terminal villi.
 Vena umbilicalis impar
 Right and Left Umbilical Vein
 Enter their corresponding cardiac
sinual horns lateral to the
terminations of the vitelline veins.
Hill, MA
2017 Embryology Kollmann5
12. jpg . Retrieved December
22, 2017, from
https://embryology.med.uns
w.edu.au/embryology/index.
php/File:Kollmann512.jpg

18.  Around 5th week of development the right umbilical vein retrogresses
completely.
 The left umbilical vein retains some vessels discharging directly into the
sinusoids, but new enlarging connections with the left half of the subhepatic
intervitelline anastomosis emerge.
 The latter is the start of a bypass channel for the majority of the placental
blood, which continues through the median ductus venosus
 Finally the right half of the subdiaphragmatic anastomosis, to reach the
termination of the inferior vena cava.

19. 3. Ductus Venosus
 Direct continuation of the umbilical vein and
arises from the left branch of the portal vein,
directly opposite the termination of the
umbilical vein.
 Connects the midpoints of the
subdiaphragmatic and subhepatic
anastomoses between the right and left
vitelline veins.
 Axial vessel during the early symmetric phase
of liver development.
 Sphincter mechanism
 It passes for 2–3 cm within the layers of the
lesser omentum, in a groove between the left
lobe and caudate lobe of the liver, before
terminating in either the inferior vena cava, or
in the left hepatic vein immediately before it
joins the inferior vena cava.

20. 4. IVC
 Right half of the Subdiaphragmatic
anastomoses.
 Parts of the left branch of the umbilical
vein, proximal and distal to their
junctions, function as branches of the
portal vein, carrying oxygenated blood
to the right and left parts of the liver.
 Blood in the left umbilical vein
therefore reaches the inferior vena cava
by three routes:
 via the hepatic veins;
 circulates through the liver with portal
venous blood
 ductus venosus (80%)

21. 5. Right Atrium
 Right atrial pressure is much
greater than left atrial pressure,
it forces the flap-like valve of
the septum primum to the left,
which permits passage of blood
from the right to the left atrium.
 The valve of the inferior vena
cava is so placed as to direct
75% of the richly oxygenated
blood from the umbilical vein
to the foramen ovale and left
atrium, where it mingles with
the limited venous return from
the pulmonary veins.

22. 6. Left Atrium
7. Left Ventricle
8. Aorta

23. 9. Umbilical
Arteries
 In direct continuation with the internal
iliac arteries.
 Thickening of the tunica media
 Before birth there is a proliferation of
connective tissue within the vessel
wall.
 The umbilical vessels constrict in
response to handling, stretching,
cooling and altered tensions of
oxygen and carbon dioxide.
 Umbilical vessels are muscular, but
devoid of a nerve supply in their extra-
abdominal course.

24. Right Ventricular Circulation
 Blood from the head and upper limbs
returns to the right atrium via the superior
vena cava, flows through the right
atrioventricular orifice into the right
ventricle.
 Pulmonary Trunk
Ductus arteriosus
directly to the aorta
 The mixture descends in the aorta and
most is returned via the umbilical arteries
to the placenta: some is distributed to the
lower limbs and the organs of the
abdomen and pelvis.

25. Ductus Arteriosus
 It is 8–12 mm long, and
 joins the aorta at an angle of
30–35º on the left side,
anterolaterally, below the
origin of the left subclavian
artery.
 In the neonate, the ductus
arteriosus is closely related to
the left primary bronchus
inferiorly and the thymus
gland anteriorly.
 Histology similar to Muscular
Artery (relation to RLN)
 Contraction prevented by
Prostaglandins E2, I2 and F2a.

27. Transition From Extra-Uterine
Life To Intrauterine Life
 Essential components for a normal neonatal transition
• Clearance of fetal lung fluid
• Surfactant secretion, and breathing
• Transition of fetal to neonatal circulation
• Decrease in pulmonary vascular resistance and increased
pulmonary blood flow
• Endocrine support of the transition

28.  Mechanical compression of
the chest during the vaginal
birth forces approximately
1/3 of the fluid out of the
fetal lungs. As the chest is
delivered, it re-expands,
generating a negative
pressure and drawing air
into the lungs.
 Passive inspiration of air
replaces fluid.
 As the infant cries, a positive
intrathoracic pressure is
established which keeps the
alveoli open, forcing the
remaining fetal lung fluid
into the lymphatic
circulation.
Pulmonary Adaptations

29. Changes with the first breath
 With the infant’s
first breath and
exposure to
increased oxygen
levels, there is an
increased blood
flow to the lungs.
 Umbilical cord
clamping decreases
oxygen
concentration,
increases carbon
dioxide
concentration, and
decreases the blood
pH.
 This stimulates the
fetal aortic and
carotid
chemoreceptors,
activating the
respiratory centre in
the medulla to
initiate respiration.

30. Removal of Placental source
 The clamping of the umbilical cord eliminates the placenta as a reservoir for blood, triggering
an increase in systemic vascular resistance (SVR), an increase in blood pressure, and increased
pressures in the left side of the heart.
 The removal of the placenta also eliminates the need for blood flow through the ductus
venosus, causing functional elimination of this fetal shunt.
 Systemic venous blood flow is then directed through the portal system for hepatic circulation.
 Umbilical vessels constrict, with functional closure occurring immediately. Fibrous infiltration
leads to anatomic closure in the first week of life.
 Temperature change and Bradykinins.

31. Umbilical Arteries
After the cord is severed the umbilical
arteries contract, preventing significant
blood loss; thrombi often form in the
distal ends of the arteries. The arteries
obliterate from their distal
ends until, by the end of the second or
third postnatal month, involution
has occurred at the level of the superior
vesical arteries. The proximal
parts of the obliterated vessels remain as
the medial umbilical
ligaments.

32. Umbilical Vein and Ductus Venosus

33. Closure of Foramen Ovale
 Decrease in pressure also occurs
in the inferior vena cava
 Atrial pressures become equal
and the valvular foramen ovale
is closed by apposition, and
subsequent fusion, of the
septum primum to the rims of
the foramen.
 Contraction of the atrial septal
muscle, synchronized with that
in the superior vena cava,
 Although the foramen ovale
closes functionally after
pulmonary respiration is
established,
 It is obliterated in fewer than 3%
of infants 2 weeks after birth,and
in 87% by 4 months after birth.

34. Closure of Ductus Arteriosus
 starts to close immediately
after birth
 attributed to increased
oxygen tension.
 A neural factor may also be
involved: the muscular wall
has afferent and efferent
nerve endings and responds
to adrenaline and
noradrenaline.
 Removal of Placenta and
Prostaglandins.
 The first stage of ductal
closure is completed within
10–15 hours
 and the second stage takes
2–3 weeks.
Stage 1
(10-15 hrs)
Functional
Stage 2
(2-3 weeks)
Anatomical
contraction
of the smooth
muscle cells and
development of
subendothelial
oedema.
Destruction of the
endothelium and
proliferation of the
intima

35. Fetal and Neonatal heart
 Situated midway between the crown of the head and the lower level of the buttocks.
 Fetal: foramen ovale lies at the level of the third intercostal space
 It is almost exactly in the coronal plane of the body
 At birth, the average thicknesses of the lateral walls of both the ventricles are
approximately equal (5 mm).

36. Summary

38. Clinical Correlations

40. Patent Foramen Ovale

41. Persistent Pulmonary Hypertension
Of The Newborn

43. Umbilical Artery Cateterization
 In order to keep the catheter
patent, a small volume of fluid
is continuously infused through
it.
 the tip of the catheter should
be located well away from
arteries branching from the
aorta.
 ‘high’ position’, above the
coeliac artery but well below
the ductus arteriosus
 ‘low’ position, below the renal
and inferior mesenteric arteries
but above the point where the
aorta bifurcates into the two
common iliac arteries.