The first symptom to be noticed in a three year old baby with roundworms may be the presence of roundworms in the stool. Roundworms parasitize within the intestines and absorb nutrients from the body, potentially causing the baby to experience slowed growth and development. Roundworms parasitized within the intestines may also cause abdominal pain. If there are more roundworms, causing intestinal obstruction, the symptoms of this abdominal pain are even more obvious. Roundworms burrowing around and into the appendix or into the bile duct may cause severe abdominal pain. So all these symptoms are possible in a three year old baby with roundworms. A rarer symptom is to spit out the roundworms, because more cases of roundworms can burrow into the stomach, and then the roundworms can be spit out with the baby’s vomiting, but the probability of this occurring is lower than those symptoms above.