Amniotic fluid acetylcholinesterase isoenzyme patterns in the diagnosis of neural tube defects.

Acetylcholinesterase isoenzyme patterns were determined in amniotic fluid from 140 normal pregnancies and from 68 pregnancies with various fetal abnormalities. A fast acetylcholinesterase isoenzyme was detected in all cases of neural tube defect, exomphalos and intrauterine death. The fast isoenzyme was not seen in any of the normal pregnancies. Blood-contaminated amniotic fluids with false positive elevation of alphafetoprotein gave a single isoenzyme band. The qualitative demonstration of a fast acetylcholinesterase isoenzyme in amniotic fluid provides a useful adjunct to the alphafetoprotein assay in the prenatal diagnosis of neural tube defects.