The clear liquid that babies spit up is saliva and formula or breast milk, according to Children's Health Network. It is usually a bit of the contents of her stomach after a feeding.
Spitting up is called reflux or gastroesophageal reflux, notes Children's Health Network. Babies often spit up after they have been fed. It usually occurs with a burp, and it does not harm the baby or cause her to cry. The clear liquid is usually saliva, while a milky-white liquid is formula or breast milk. Spitting up is only a problem if the baby is spitting up often enough to interfere with nutrient intake and weight gain.