Which of the following is the main factor for the ductal closure postnatally

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