Describe the Fetal circulation and mention that changes that accur in it at placental stage and after birth.

1. FOETAL CIRCULATION
MS. MUNEERA MAKRANI
ASSISSTANT PROFESSOR
DEPT. OF OBSTETRICS AND
GYNAECOLOGICAL NURSING

3. • THE FOETUS: It is the term use to refer to a prenatal mammal
between it’s embryonic state and it’s birth.
• THE PLACENTA: The organ in human mother responsible for
the supplying for oxygen and nutritive material to the fetus and
for the elimination of CO2 and Nitrogenous waste out of the
fetus.

4. • THE UMBILICAL CORD: A flexible cord like structure
containing blood vessels and attaching a human to the placenta
responsible for the supplying and elimination of O2 and CO2.
• THE FOETAL CICULATION: The circulation of oxygenated
blood, de-oxygenated blood, nutritive material etc. in the fetus is
termed as “Fetal Circulation”.

5. ❑ ROLE OF PLACENTA IN FETAL CIRCULATION:
✓The circulatory system of the mother is not directly
connected to that of the fetus, so the placenta functions as
the Respiratory Centre for the fetus as well as a site of
filtration for plasma nutrients and wastes, water, glucose,
amino acids, vitamins, and inorganic salts freely diffuse
across the placenta along with oxygen.
✓The uterine artery carry oxygenated blood to the
placenta.

6. ❑ FOETAL LUNGS:
• Pulmonary vascular resistance is the resistance offer to blood
through lungs. The resistance is very high in fetus because of
the non-functioning of the fetus lungs. Because of the high
pressure the lungs, the blood is diverted from the pulmonary
artery into aorta.

7. ❑ BLOOD VESSELS IN THE FETUS:
• The blood vessels responsible for fetal circulation are-
✓ Umbilical Vein
✓Umbilical Arteries

8. ✓ UMBILICAL VEIN:
• It carry the oxygenated blood (80% saturated) from the
placenta, to the growing fetus.
• The blood pressure in the umbilical vein is approximately 20
mmhg.

9. ✓ UMBILICAL ARTERY:
• It is the paired artery that is found in the pelvic and abdominal
region of the fetus which extends into the umbilical cord.
• Supplies de-oxygenated blood from the fetus to the placenta.

10. ❑ SHUNTS INVOLVED IN FOETAL CICULATION:
• There are Three shunts present in the fetus.
• They are:
1 Ductus Venosus
2 Ductus Arteriosus
3 Foramen Ovale

11. 1 Ductus Venosus:
• The ductus venosus shunts the portion of the left umbilical vein
blood flow directly to the Inferior Vena Cava (IVC).
• Allowed oxygenated blood from the placenta to bypass the liver.
2 Ductus Arteriosus:
• Also called the “Ductus Botalli”.

12. • Connect the pulmonary artery to the proximal descending artery.
• It allows the most of blood from the Right-ventricle to bypass
the fetus fluid-filled Non-functioning lungs.
3 Foramen Ovale:
• It is the opening in the intra arterial septum.
• It allows the blood to enter the left atrium from the right atrium.
• It is also called “False Septi”.

15. • The umbilical vein carrying the oxygenated blood from the
placenta, enter the fetus at the umbilicus and runs along with
free margin of falciform ligament of the liver.
• In the liver, it gives off branches to the left lobe of the liver and
receives the deoxygenated blood from the portal vein.
• The greater portion of the oxygenated blood, mixed with portal
venous blood, short circuits the liver through the Ductus

16. Venosus to enter the IVC and thence to right atrium of the heart.
• The O2 content of this mixed blood is thus reduced.
• Although both the ductus venosus and hepatic portal/ fetal trunk
bloods enter the right atrium through the IVC, there is little
mixing.
• The terminal part of the IVC receives blood from the right
hepatic vein.

17. • In the right atrium, most of the well oxygenated (75%) ductus
venosus blood is preferentially directed into the foramen ovale
by the valve of the inferior vena cava and crista dividens and
passes into the left atrium.
• Here it is mixed with small amount of venous blood returning
from the lungs through the pulmonary veins.

18. • This left atrial blood is passed on through the mitral opening
into the left ventricle.
• Remaining lesser amount of blood (25%), after reaching the
right atrium via the superior and inferior vena cava (carrying the
venous blood from the cephalic and caudal parts of the fetus
respectively) passes through the tricuspid opening into the right
ventricle.

19. • During ventricular systole, the left ventricle blood is pumped
into the ascending and arch of aorta and distributed by their
branches to the heart, neck, brain and arms.
• The right ventricular blood with low oxygen content is
discharged into the pulmonary trunk.

20. • Since the resistance in the pulmonary arteries during fetal life is
very high , the main portion of the blood passes directly through
the ductus arteriosus into the descending aorta bypassing the
lungs where it mixes with the blood from the proximal aorta.
• 70% of cardiac output (60% from right and 10% from left
ventricle) is carried by the ductus arteriosus to the descending
aorta.

21. • About 40% of combined output goes to the placenta through the
umbilical arteries.
• The deoxygenated blood leaves the body by the way to two
umbilical arteries to reach the placenta where it is oxygenated
and gets ready for circulation.

22. • The mean cardiac output is comparatively high in fetus and is
estimated to be 350 ml par kg per minute.

23. ❑ CHANGES OF THE FOETAL CIRCULATION AT BIRTH:
• The haemodynamics of the fetal circulation undergoes profound
changes soon after birth due to-
1 Cessation of the placental blood flow and
2 Initiation of respiration
• The following changes occur in the vascular system:
1 Closure of the umbilical arteries
2 Closure of the umbilical vein
3 Closure of the ductus arteriosus
4 Closure of the foramen ovale

24. 1 CLOSURE OF THE UMBILICALARTERIES:
• Functional closure is almost instantaneous preventing even
slight amount of fetal blood to drain out.
• Actual obliteration takes about 2-3 months.
• The distal parts from the lateral umbilical ligaments and the
proximal parts remain open as superior vesical arteries.

25. 2 CLOSURE OF THE UMBILICAL VEIN:
• The obliteration occurs a little later than arteries, allowing few
extra volume of blood (80-100 ml) to be received by the fetus
from the placenta.
• The ductus venosus collapses and the venous pressure of the
IVC falls and so also the right arterial pressure.
• After obliteration, the umbilical vein forms the ligamentum
teres and ductus venosus becomes ligamentum venosum.

26. 3 CLOSURE OF THE DUCTUS ARTERIOSUS:
• Within few hours respiration, the muscle wall of the ductus
arteriosus contracts probably in response to rising oxygen
tension of the blood flowing through the duct.
• The effects of the variation of the O2 tension on the ductus
arteriosus are thought to be mediated through the action of
prostaglandins.

27. • Prostaglandin antagonists given to the mother may lead to the
premature closure of the ductus arteriosus.
• Whereas functional closure of the ductus may occur soon after
the establishment of pulmonary circulation, the anatomical
obliteration takes about 1-3 months and becomes ligamentum
arteriosum.

28. 4 CLOSURE OF THE FORAMEN OVALE:
• This is caused by increased pressure of the left atrium
combined with a decreased pressure on the right atrium.
• Functional closure occurs soon after birth but anatomical
closure occurs in about 1 year time.
• During the first few days, the closure may be reversible.

29. • This is evidenced clinically by the cyanotic look of the baby
during crying when there is shunting of the blood from right to
left
• Within one or two hours following birth, the cardiac output is
estimated to be about 500 ml per minute and the heart rate
varies from 120-140 per minute.

32. THANK YOU