The Pediatrician Answers:
a) If the baby spits up a small stain with almost every feeding, is gaining weight well, and is not having any lung problems, then that spitting is normal.
b) If the baby is spitting more than an ounce (covers the area of a large dinner plate or more) with each feeding, and is not gaining weight well or is having lung problems (wheezing, chronic bronchitis, persistent wet cough), that is abnormal, and is probably gastro-esophageal reflux (GER). This usually requires medication.
c) All the situations in-between? Consult your practitioner, but if the child is gaining weight, then there is usually not serious disease.