How long should new born babies spit up mucus?

Spitting Mucus. Hello! Newborns may spit up mucus leftover from amniotic fluid up to 72 hrs after birth but tends to resolve sooner. If the saliva seems excessive, a doc visit is needed to check for issues of the esophagus. Spitting up milk is also common in newborns and should be discussed with your doc to ensure it's normal infant reflux. For future consults, my link is PNYTKV. .