I have never met a baby that didn't on occasion spit-up. Many perfectly healthy babies can even spit-up quite a bit. Reflux is often the label given to babies who vomit, and this rarely amounts to a significant problem.
However, there are a few things that a parent should watch out for:
The most important thing is the color of what a baby is throwing up. Dark yellow and especially green vomit is never normal in a baby and demands immediate medical evaluation as this could represent a dangerous twisting of the intestines (midgut volvulus), which is linked to abnormally positioned intestines (intestinal malrotation).
Another consideration is quantity. If a baby is throwing up...