Acetylcholinesterase and fetal malformations: modified qualitative technique for diagnosis of neural tube defects.

A single-blind study involving amniotic-fluid samples from 214 pregnancies of known outcome confirms that an electrophoretically distinct isoenzyme of acetylcholinesterase is associated with fetal open neural tube defects. Furthermore, only one of 13 amniotic-fluid samples with false-positive results for alpha-fetoprotein showed the characteristic isoenzyme, indicating that qualitative acetylcholinesterase assessment can decrease the proportion of false positives from the alpha-fetoprotein assay. We have also identified this characteristic isoenzyme in amniotic fluids from pregnancies in which other serious fetal defects occurred. A detailed electrophoresis protocol for identifying this characteristic isoenzyme is described.