system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Accurate diagnosis of anencephaly on ultrasound can be done at: September 2005
assistant
The correct answer is  Ans. C: 10 weeks of gestation In the first half of the pregnancy, the diagnosis is made by the elevated alfa-fetoprotein in amniotic fluid and confirmed by sonography. The findings at 13 weeks are: Absence of cranial vault Angiomatous brain tissue In the later half of the pregnancy the diagnosis is difficult specially when associated with hydramnios.