## **Core Concept**
The question pertains to the differential diagnosis of vomiting in a newborn on the first day of birth. This requires knowledge of conditions that can cause early neonatal vomiting, which can be due to various gastrointestinal, metabolic, or infectious causes.

## **Why the Correct Answer is Right**
The correct answer, **D. Hirschsprung's disease**, typically presents with symptoms later than the first day of life. Hirschsprung's disease is a congenital condition characterized by the absence of ganglion cells in the distal bowel, leading to a functional obstruction. Symptoms usually become apparent in the first few days of life, with abdominal distension and failure to pass meconium being common initial presentations, rather than immediate vomiting on the first day.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While the specifics of option A are not provided, conditions like pyloric stenosis can cause vomiting early in life, often within the first week, but typically not immediately on the first day.
- **Option B:** Similarly, without specifics, certain metabolic disorders can indeed cause early onset vomiting.
- **Option C:** Again, without details, some infections or gastrointestinal anomalies could present with vomiting on the first day.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that while Hirschsprung's disease can cause vomiting, it usually does so after the first 24-48 hours of life, alongside other symptoms like abdominal distension and failure to pass meconium. Early onset vomiting in a newborn can be due to a variety of causes including infection, metabolic disorders, and anatomical obstructions.

## **Correct Answer:** D. Hirschsprung's disease.