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
Which of the following tests on maternal serum is most useful in distinguishing between open neural tube defects and ventral wall defects in a fetus? 
Select and explain. 
A. Carcinoembryogenic antigen, B. Sphingomyelin, C. Alpha-feto protein, D. Pseudocholinesterase
D: Pseudocholinesterase
Answer: D: Pseudocholinesterase 
Explanation: In patients with elevated amniotic fluid AFP to differentiate between NTD and abdominal wall defect, acetylcholinesterase and pseudocholinesterase are measured: