Isoelectric focusing pattern of human amniotic fluid alpha-fetoprotein.

Isoelectric focusing (IEF) of amniotic fluid alpha-fetoprotein (AFP) in thin-layer polyacrylamide gels containing 8 M urea followed by immunoblotting reveals at least nine bands, band I lying next to the cathode. Compared with 298 amniotic fluid samples from normal pregnancies, we found that the density of band V was increased in seven cases of fetal death. In 16 amniotic fluid samples from pregnancies with open neural tube defects (ONTD), band V disappeared or was markedly decreased. In seven cases with elevated AFP and positive acetylcholinesterase (AChE) due to contamination with fetal blood, no difference in pattern was observed compared with samples from normal pregnancies. It is suggested that IEF of AFP and subsequent immunoblotting are an apparently diagnostic test for ONTD and intrauterine fetal death (IUFD).