Healthy people have the spores of this fungus in their mouths. Babies can pass oral thrush on through breastfeeding. This can cause nipple thrush in mothers. These healthy bacteria normally help … Oral thrush may occur in babies because their immune systems have not yet matured. Mothers who have had a vaginal yeast infection while pregnant or during delivery can pass the infection to their baby in the form of oral thrush. Oral thrush is caused by the yeast Candida albicans. Because the main cause of oral thrush is a weak immune system, babies develop it most frequently – their immunity is … Another possible cause for oral thrush infection is if your baby has had a recent course of antibiotic medication. Causes of oral thrush in babies Oral thrush is caused by a group of yeasts called Candida. This is because the antibiotics can kill off healthy germs (bacteria) that live in your baby's mouth. It doesn't normally cause problems. An oral thrush infection … If you're not sure it's oral thrush Look at other causes of a white or sore tongue. They are less able to resist infection. We’ve all got this yeast in our bodies, and it normally lives in balance with other organisms. Oral thrush is normally caused by a common oral fungus, candida albicans. This is probably an infection caused by a type of yeast called Candida albicans, and it’s better known as thrush when it’s in the mouth… Causes of Oral Thrush in Babies Babies may develop oral thrush for a number of reasons, but mainly because their immune system is not fully developed and cannot fight off certain organisms. Take a deep breath. Your baby has got every right to shout. Causes of oral thrush Thrush can occur in the throat, tongue and moist lining of your baby’s mouth.