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How does birth change the path of blood flow through the heart and lungs?
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human development
Growth of the human fetus from the fourth month to the ninth month of pregnancy.
At birth, the transition from fetal to independent circulation involves critical structural changes that redirect blood flow through the lungs. During fetal development, the ductus arteriosus and the foramen ovale act as shunts that allow blood to bypass the non-functional, fluid-filled lungs.12
When a newborn takes its first breaths, the lungs inflate and intrapulmonary fluid is evacuated. This process triggers several key changes:3
- Pulmonary Circulation: As the lungs fill with air, the pulmonary circulation opens to accept the full cardiac output, which was previously bypassed.3
- Ductus Arteriosus Closure: This channel, which connects the pulmonary artery to the aorta, normally closes shortly after birth, effectively separating the pulmonary and systemic circulations.1
- Foramen Ovale Closure: The opening between the two atria of the heart also closes, ensuring that deoxygenated blood is directed to the lungs for oxygenation rather than bypassing them.2
These adjustments allow the newborn to transition from receiving oxygen via the placenta to utilizing their own respiratory system.14