Amniotic fluid cholinesterase measurement as a rapid method for the exclusion of fetal neural tube defects.

Amniotic fluid total cholinesterase (ChE) and acetylcholinesterase (AChE) activities have been measured in 404 pregnancies without fetal malformation and 79 pregnancies associated with open neural-tube defects (NTDs). Neither measurement, either alone or in combination, gave complete separation of the two groups. However, measurement of ChE can be used to assess the probability that a woman is carrying a fetus with an open NTD. Since ChE can be measured within 15 minutes and shows at least 70% of women selected for amniocentesis by serum alpha-fetoprotein screening to have a less than 1 in 100 chance of carrying a fetus with an open NTD, we suggest that this test may be used in an amniocentesis clinic both to reassure women with normal pregnancies and to select probable abnormalities for immediate further investigation.