Which of the following is the main factor for the ductal closure postnatally: (A) Increase in paial pressure of oxygen (PaO2), (B) Increase in systemic vascular resistance, (C) Increase in circulating prostaglandin levels, (D) Decrease in pulmonary venous resistance
Answer is A. Oxygen is the most impoant controlling ductal closure. Note: Gestational age also appears to play an impoant role; the ductus of a premature infant is less responsive to oxygen, even though its muscular is developed. Hence, patent ductus aeriosus (PDA) is more common in premature infants. Ref: Nelson textbook of pediatrics 21st edition Pgno: 2345