Prospective prenatal screening for fetal abnormalities using a quantitative immunoassay for acetylcholinesterase.

An immunoassay based on a monoclonal antibody specific for acetylcholinesterase (AChE) was used prospectively over a two year period to screen second trimester amniotic fluids for fetal abnormalities. All 26 cases of spina bifida, three of which had normal alphafetoprotein (AFP) concentrations and ultrasound scans, were detected by the immunoassay. Four clear fluids, with abnormal AFP concentrations, had normal AChE titres and yielded normal outcomes. Some difficulties were encountered with both the AChE immunoassay and polyacrylamide gel testing when amniotic fluids were contaminated with old blood. However, the quantitative nature of the AChE immunoassay and its independence of operator experience make it an ideal adjunct to AFP assay for routine screening of amniotic fluids.