Acetylcholinesterase Presence of acetylcholinesterase (AChE) in the amniotic fluid is seen in cases of fetal open neural tube defects (NTD). It has got a better diagnostic value than AFP. Acetylcholinesterase (AchE) a neural enzyme is present in cerebral spinal fluid and fetal blood. AChE is not normally detectable in amniotic fluid. AChE in amniotic fluid can also be seen in cases of ventral wall defect, fetal demise (including demise of a co-twin) and massive fetal blood contamination. When AChE is detected, the ratio of AChE to pseudocholinesterase (PChE), a non-specific cholinesterase normally found in amniotic fluid, may help distinguish open neural tube defects from open ventral wall defects. The levels of AChE are higher in open NTD than ventral wall defects. Ratio greater than 0.15 - open spna bifida Ratio less than 0.10 - ventral wall defect