This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Genetics, Subject name: Medicine
[{'content': "Alpha-fetoprotein in maternal serum and/or amniotic fluid is increased in all except \nSelect and explain. \nA. Fetal neural tube defects, B. Down's syndrome, C. Anencephaly, D. Encephalocele", 'role': 'user'}, {'content': "Answer: B \nExplanation: In Down syndrome, the AFP is decreased in the mother's blood, presumably because the yolk sac and fetus are smaller than usual. Estriol is a hormone produced by the placenta, using ingredients made by the fetal liver and adrenal gland. Estriol is decreased in the Down syndrome pregnancy Ref Robbins 9/e pg 170", 'role': 'assistant'}]