Accurate diagnosis of anencephaly on ultrasound can be done at: September 2005: (A) 5 weeks of gestation, (B) 8 weeks of gestation, (C) 10 weeks of gestation, (D) 14 weeks of gestation
Answer is C. 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.