The document summarizes fetal circulation during pregnancy. The fetus receives nutrition and oxygen from the mother through the placenta and umbilical cord. Blood from the umbilical vein carries oxygen to the fetus, with 50% entering the liver and 50% bypassing to the inferior vena cava. This blood then mixes with lower fetal blood and passes through the foramen ovale into the left ventricle to supply the brain and upper body. After birth, closure of the ductus arteriosus, foramen ovale, and ductus venosus support the transition to normal circulation.

2. Introduction
During pregnancy, fetus depends upon its mother for
nutrition and oxygen
Blood circulation is different than it is after birth
All the necessary nutrition, oxygen and life support
from mother goes through the placenta and to the
fetus through blood vessels in the umbilical cord

4. Circulation Pathway
Umbilical vein carries oxygenated blood and
arteries carry deoxygenated blood
50% of the umbilical venous blood enters the hepatic
circulation
50% bypasses the hepatic circulation and enters
inferior vena cava via Ductus Venosus

5. Cont’d
Here it mixes with the poorly oxygenated blood from
the lower fetal part.
This blood enters the right atrium and flows to the left
atrium via foramen ovale.
From left atrium, it flows into the left ventricle and via
ascending aorta goes to the fetal upper body and
brain

6. Cont’d
Fetal Superior vena cava enters the right atrium,
bypasses the left atrium and enters blood into right
ventricle
From the right ventricle, blood is ejected via pulmonary
artery into lungs
The major portion of this blood bypasses the lungs and
flows right to left through the ductus arteriosus into the
descending aorta to perfuse the lower part of the fetal
body including flow to the placenta via two umbilical
arteries

7. Fetal circulation
Three cardiovascular
structures are unique to
fetal circulation that are
important for maintaining
parallel circulation:
1. Ductus Venosus
2. Ductus Arteriosus
3. Foramen Ovale

8. Total fetal cardiac output is 450ml/kg/min
Approx 65% of fetal blood in descending aorta
returns to the placenta. The rest of 35% perfuses the
fetal organs and tissues

9. The transition from fetal
circulation
A fall in pulmonary resistance after the first few
breaths
Removal of low resistance placental circulation leads
to an increase in systemic vascular resistance
A fall in pulmonary arterial pressure

10. Cont’d
Because pulmonary resistance becomes lower than
systemic resistance, the shunt through ductus
arteriosus reverses and becomes left to right.
The high arterial pressure first constricts and then
closes the ductus arteriosus. It becomes
Ligamentum arteriosum

11. Cont’d
The increased volume of pulmonary blood flow
returning to the left atrium from the lungs, increases
the left atrial volume and pressure sufficiently to
close the foramen ovale.
Removal of the placenta from circulation also closes
the ductus venosus

13. SUMMARY OF BLEEDING
DISORDERS
Condition PT APTT BT PLATELETS
1 N N
2 N N N
3 N N N
4 N N
5 N N N
6 N N
7
8 N N N N

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