This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Gynaecology & Obstetrics
Alpha fetoprotein levels are increased in all EXCEPT: 
Select and explain. 
A. Open neural tube defects, B. Twin pregnancy, C. Intrauterine death, D. Down syndrome
D: Down syndrome
Answer: D: Down syndrome 
Explanation: AFP is measured in pregnant women through the analysis of maternal blood or amniotic fluid,
as a screening test for a subset of developmental abnormalities: it is principally increased in open neural tube defects and omphalocele and is decreased in Down syndrome.