Which statement about events after birth is false?

• A. Systemic pressure increases
• B. Pulmonary vascular resistance increases
• C. Right heart pressure decreases
• D. Foramen ovale closes

Answer: (B)

After birth, the circulatory system shifts from fetal to neonatal circulation. In fetal life the lungs are not inflated and pulmonary vascular resistance (PVR) is high, so most blood bypasses the lungs via right-to-left shunts like the foramen ovale and ductus arteriosus. Once the baby takes breath, the lungs inflate, oxygen tension rises, and mediators promote pulmonary vasodilation, causing PVR to fall dramatically. This increase in pulmonary blood flow lowers right heart afterload and raises left-sided return. Meanwhile, clamping the umbilical cord removes the low-resistance placental circuit, so systemic vascular resistance rises. The higher pressure on the left side compared with the right drives the closure of the foramen ovale. Ductus arteriosus also constricts under higher oxygen and lower prostaglandins. Therefore, the statement that pulmonary vascular resistance increases after birth is false; PVR actually decreases as circulation shifts to the lungs.