what causes thrush in newborns
Oral thrush occurs when a yeast infection develops on the inside of your mouth and on your tongue. This condition is also known as oropharyngeal candidiasis. The Candida albicans fungus causes oral thrush. A small amount of this fungus normally lives in your mouth without causing harm. However, when the fungus begins to grow uncontrollably, an infection can develop in your mouth. Oral thrush most often occurs in infants and toddlers.
1 The infant may refuse to eat, which can be mistaken for lack of hunger or poor milk supply. If the infant is unable to eat because of a sore mouth or throat, he or she may act fussy.  Diaper rash, which may develop because the yeast that causes thrush also will be in the baby's stool.