This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetic Approach to Pediatric Medicine, Subject name: Pediatrics
[{'content': 'The earliest congenital anomaly identified by ultrasound is: \nSelect and explain. \nA. Hydrocephalus, B. Encephalocele, C. Spina bifida, D. Anencephaly', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. (d) AnencephalyRef.: Nelson 18th ed./Ch. 592.6* Anencephaly is absence of cranial vault posteriorly with brain and meninges exposed.This condition can be detected by antenatal USG as early as 11-12 weeks.', 'role': 'assistant'}]