Transitional Changes After Birth ✅ Flashcards
What happens to foetal circulation at birth?
Circulation through the placenta ceases
What happens to the lungs at birth?
They inflate
What happens to the foetal circulatory shunts at birth?
They are no longer necessary and cease to function
How long do changes occurring as a foetus transitions to independent life take?
Some occur with the first breath, some take place over hours or days
Are the changes that occur when a foetus transitions to independent life functional or structural?
Initially functional, followed by definitive anatomical changes
What effect does removal of the placenta have on foetal circulation?
- Increases systemic vascular resistance
- Closure of the ductus venosus
Why does removal of the placenta lead to a closure in the ductus venosus?
Due to cessation of the blood flow in the umbilical veins
Where does blood pass through the liver once the ductus venosus has closed?
Through the hepatic sinusoids
What does the ductus venosus become?
The ligamentum venosum
Where does the ligamentum venosum pass?
Through the liver form the left branch of the portal vein to the IVC, to which it is attached
What does lung expansion and aeration cause?
An increase in alveolar oxygen tension
What does the increase in alveolar oxygen tension cause?
A rapid fall in pulmonary vascular resistance
Why does the increase in alveolar oxygen tension cause a rapid fall in the pulmonary vascular resistance?
Due to the vasodilatory effect of oxygen on the pulmonary vasculature
What happens to the pressure in the left atrium after birth?
It falls to below the left atrium
Why does the pressure in the right atrium fall after birth?
- Increased pulmonary blood flow
- Removal of the placenta decreasing right atrial return and increasing systemic vascular resistance
What is the result of the left atrial pressure exceeding the right atrial after birth?
There is a functional closure of the foramen ovale
When does anatomical closure of the foramen ovale occur?
By 3 months
How is anatomical closure of the foramen ovale achieved?
The valve fuses with the septum premium and the intertribal septum becomes a complete partition between the atria
What remains after anatomical closure of the foramen ovale?
The fossa ovale
What is the fossa ovale?
An oval depression in the lower part of the interatrial septum
What changes in the circulation occur 6-8 weeks after birth?
There is a second, slower fall in the pulmonary vascular resistance and pulmonary artery pressure
What causes the fall in pulmonary vascular resistance and pulmonary arterial pressure 6-8 weeks after birth?
Thinning of the pulmonary arterioles
What causes the closure of the ductus arteriosus?
- Increase in prostaglandin E2 (PGE2) metabolism
- Increase in arterial oxygen concentration
- Increase in bradykinin and other vasoactive substances
What causes the increase in bradykinin and other vasoactive substances in a newborn?
The increase in oxygen content of aortic blood
What % of term neonates have functional closure of the ductus arteriosus within 24 hours?
50%
What % of term neonates have functional closure of the ductus arteriosus within 48 hours?
75%
What % of term neonates have functional closure of the ductus arteriosus within 96 hours?
Close to 100%
When does anatomical closure of the ductus arteriosus occur?
By 3 months of age
When might there be a delay in closure of the ductus arteriosus?
Preterm infants
When might a delayed closure of the ductus arteriosus be induced?
In duct-dependent congenital heart disease
How can closure of the ductus arteriosus be delayed?
By infusing prostaglandin E2
When might the pulmonary vascular resistance not fall as usual with the infants first breaths?
- Perinatal asphyxia
- Neonatal hypothermia
- Sepsis
- Meconium aspiration
What is it called when the pulmonary vascular resistance doesn’t fall with the infants first breaths?
Persistent pulmonary hypertension of the newborn (PPHN)
What effect does PPHN have on shunts?
The fetal pattern of right to left shunting across the foramen ovale and ductus arteriosus persists
What does the persistence of right to left shunting across the foramen ovale and ductus arteriosus in PPHN lead to?
Intrapulmonary shunting and further hypoxia and acidosis
