Because of the beneficial effect of corticosteroids on
lung function, especially in
infants who are ventilator dependent, corticosteroids are, at times, administered to very low birth weight neonates to treat established or evolving
lung disease.
But it is thought that the sudden drop in prostaglandin blood levels after birth (much of the prostaglandins was made in the
infants placenta), an increase in the
infants blood oxygen level as its
lungs begin to
function and decreased resistance to blood flow as the
infant's
lungs fully expand drive the closure process.