Amniotic Fluid Constituents, Cell Culture, and Neural Tube Defects

Analysis of the chemical constituents of amniotic fluid (AF) has yielded valuable information for prenatal diagnosis, allowing assessment of fetal physiology and metabolism. Because the AF can be viewed as an extension of the fetal extracellular space, an understanding of its origin, formation, and chemical constitution is crucial to prenatal diagnosis and fetal therapy. This chapter lists various nonenzymatic constituents and characteristics of AF. Elevated values of biochemical constituents in AF may be nonspecific, such as 5-hydroxyindole-3-acetic acid in a fetus with Cornelia de Lange syndrome or acid-soluble glycoproteins in AF in CF. Reduced amounts of 5-hydroxyindole-3-acetic acid, and increased amino acids (especially methionine, isoleucine, leucine, tyrosine, and phenylalanine) have been observed in the AF of fetuses with neural tube defects (NTDs). The chapter also provides a synopsis of the current classification of human amniotic fluid cells (AFCs) in culture.