First-trimester amniotic fluid acetylcholinesterase electrophoresis

Acetylcholinesterase (AChE) gel electrophoresis was performed on normal amniotic fluids obtained at 4–15 weeks of pregnancy. Until 8 weeks, all the fluids were AChE-positive; the percentage of positive specimens decreased from 9 until 11 weeks and no positive specimen was found after 12 weeks. This method may allow early prenatal dignosis of neural tube defects after the 12th week.