Amniotic fluid amino and nucleic acid in normal and neural tube defect pregnancies - A comparison

OBJECTIVE: To explore the relationship between fetal amino acids (AAs), whi ch are the components of structural proteins and nucleic acids, and the cha nges associated with neural tube defects (NTD). STUDY DESIGN: Ten weekly anniotic fluid (AF) samples from normal pregnancie s (non-NTD) and 10 from NTD pregnancies between 16 and 20 weeks' gestationa l age were analyzed for AAs, and the weekly average for the non-NTD and NTD groups was determined. The group mean levels were compared by ANOVA. RESULTS: The weekly group mean levels of methionine, serine rand aspartic a cid were significantly lower than the weekly group mean levels of the other AAs. The group mean levels of methionine were significantly lo lower for N TD than for non-NTD pregnancies. CONCLUSION: The mean methionine level in NTD pregnancies was the only AA al teration in NTD. Although the AF levels of the non-NTD pregnancies showed t hat the levels of serine, aspartic acid and methionine were 3- to 19-fold l ower than those of the other AAs, only methionine is essential. Consequentl y, methionine is rate limiting with respect to the role of structural prote ins and nucleic acids in the fetus.