Final answer:
The nurse should report persistent vomiting after meals to the healthcare provider, as it may indicate a health issue requiring medical attention, differing from the other options which are typical developmental behaviors or signs of healthy growth.
Step-by-step explanation:
In assessing a 3-year-old toddler at a well-child visit, the nurse should report Option 4: Persistent vomiting after meals to the provider. Occasional thumb-sucking (Option 1) is a common behavior among toddlers and does not typically require medical intervention unless it persists beyond the preschool years. A weight gain within the expected range (Option 2) signifies healthy growth and would not be a concern. Difficulty pronouncing certain words (Option 3) is also typical for toddlers as they develop language skills; however, if this difficulty is significant, a speech therapist can be consulted, but it is not usually an immediate medical concern.
A symptom such as persistent vomiting after meals could indicate a range of potential health issues, including gastrointestinal disorders or food intolerances that need to be addressed promptly by a healthcare professional. It contrasts with the more typical developmental behaviors and healthy growth benchmarks listed in the other options.