Developmental changes in amino acid concentrations in human amniotic fluid: Abnormal findings in maternal phenylketonuria

The amino acid composition of amniotic fluid samples obtained from 51 patients at various stages of fetal gestation was determined by column chromatography. There is a decreasing concentration of most of the amino acids with increasing gestational age. The maximum rate of this decrease occurs between the twenty-second and the twenty-fourth week of pregnancy. As it is well established that the offspring of women with phenylketonuria (PKU) will have in most cases intrauterine and postnatal growth retardation, mental retardation, and/or structural abnormalities, amniotic fluid samples from 2 pregnancies of a woman affected with PKU were also analyzed. In both pregnancies (eighth and fortieth weeks of gestation) the amniotic fluid phenylalanine concentration was elevated to about 35 times that of normal.