This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
[{'content': 'Congenital hypertrophic pyloric stenosis usually presents – \nSelect and explain. \nA. Within 2 days after birth, B. Around 1 week after birth, C. Around 2 weeks after birth, D. Around 2 months after birth', 'role': 'user'}, {'content': "Answer: C \nExplanation: The symptoms vomiting usually starts after 3 weeks of age but symptoms may develop as early as1st week of life and as late as 5 months of life.\xa0- Nelson\n\nCongenital hypertrophic pyloric stenosis\n\nHypertrophic pyloric stenosis is the commonest surgical disorder of the stomach during infancy.\nPylorus is thickened and elongated and its lumen is narrowed due to hypertrophy of circular muscle fibers of pylorus.\nMore common in boys.\nMore common in infants of blood group 'B' and 'O'.\nAssociated congenital defects are → Tracheoesophageal fistula and hypoplasia or agenesis of inferior labial frenulum.\nMay be associated with Turner syndrome, Trisomy 18.\nSymptoms are not present at birth.\nThe vomiting usually starts after 3 weeks of age.", 'role': 'assistant'}]