Fetal and perinatal circulation

Educative ppt for students and trainees in Paediatrics, Paediatric Critical care , Neonatology , DCH, DNB Paediatrics

2. The placenta provides the exchange of
gases and nutrients in the fetus.

3. Four Shunts :
1.The Placenta –55% of ventricular output and has
the lowest vascular resistance in the fetus.
2.SVC –15%
3.IVC –70%
4.The highest partial pressure of oxygen (PaO2) is
found in umbilical vein –32 mmHg
5.Brain and coronary arteries –receive blood with
higher oxygen saturation PaO2 of 24 mmHg

5. Lungs receive 15% of combined ventricular
output.
RV > LV
RV-55% LV –45%

6. Fetal C.O directly proportional to HR
Low compliance of Fetal Heart .

7. Primary change –Shift of blood flow from
placenta to lungs for oxygenation.
Establishment of Pulmonary circulation

8. Increase in SVR
Cessation of blood flow in the umbilical
vein
Closure of Ductus Venosus

9. Reduction in PVR
Increase in Pulmonary blood flow
Fall in PA Pressure
Functional closure of foramen ovale
Increase in LA pressure
Decrease RA pressure
Closure of PDA

11. 1.Hypoxia and /or altitude
2. RDS or Congenital Pneumonia
3. Metabolic Acidosis
4. Increased pulmonary artery pressure
secondary to VSD or PDA
5. Increased pressure in the left atrium or
pulmonary vein.

12. Infants with large VSD may not develop
CHF while living at high altitude, but
develop CHF at sea level.
In RDS, increase in PaO2 dilates
pulmonary vasculature resulting in CHF
as baby improves
CHF does not develop in VSD till 6 to 8
weeks of age or older due to high PA
pressure directly transmitted through LV
pressure.

13. Functional Closure 10 to 15 hours after
birth by constriction of the medial smooth
muscle in the ductus.
Anatomic Closure 2 to 3 weeks
permanent changes in the endothelium and
subintimal layers of the ductus.
Oxygen, PGE2 levels, and maturity of
newborn, acetylcholine and bradykinin are
important factors in the closure of the
ductus.

14. Strongest stimulus for constriction of the
ductal smooth muscle postnatal
increase in PaO2 from 25 mmHg to 50
mmHg
Ductal tissue is less responsive to the
oxygenation changes in premature infant
due to immature ductus and smooth
muscles in the media of ductus.
High levels of PGE2 in preterm infants.

15. Decrease in PGE2 levels after birth 
constriction of the ductus
Constricting effects by indomethacin and
the dilator effects of PGE2 &
Prostaglandin I2 > for premature babies
Aspirin use in mother Constricts the
ductus during fetal life can cause
PPHN.

16. Increased PGE2
Reduced arterial PaO2
Birth Asphyxia
Hypoxia due to pulmonary diseases
High altitude

17. PA constricted by
O2 and Metabolic acidosis
Epinephrine
Nor-epinephrine
PA dilated by
Vagal stimulation
Isoproterenol
Bradykinin

18. Rate at which PVR falls
Responsiveness of the ductus arteriosus
to oxygen
High circulating levels of PGE2
Early onset of a large left to right shunt
and CHF