What effect does too much antibiotics has on a baby?

Need more info: What antibiotic? How much given? What was the purpose of the medication to begin with? Go back to the doctor who prescribed this and discuss the issue before baby gets sick.

ABx side effects: The baby exposure to prolonged course or broad spectrum antibiotics has an adverse side effects on the infant's guts flora, by the inhibiting the good bacterias and promote the growth of the bad ones. It's also increasing the risk of fungal infection, including the fungal sepsis. It's also contribute to the feeding intolerance. Some of them may affect the hearing abilities. And so on and so forth.