The initials stand for transient tachypnea of the newborn.  It is also
called "wet lung".  It may occur in full terms, and thus is
distinguished from respiratory distress syndrome or hyaline membrane
disease of the prematures.  Nobody knows what causes it, but it is more
common amongst babies born by caesarean section, possibly because normal
birth is supposed to squeeze the fluid out of the baby's lungs.

If the baby has pneumonia, this is no longer ttn, however.  TTN, by
definition, would exclude pneumonia.

Jack Newman, MD, FRCPC