<prompt> Accurate diagnosis of anencephaly on ultrasound can be done at: September 20055 weeks of gestation8 weeks of gestation10 weeks of gestation14 weeks of gestation  <response>: 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. 