Maternal Hartnup disorder.

We describe childbearing in two unrelated women with Hartnup disorder, an inborn error of neutral amino acid transport. Two living, unaffected offspring born after untreated and uneventful pregnancies, one from each woman, have had normal growth and development. The older one had an IQ of 92 at 4 years while the younger one at 4 months had a Development Quotient of 107 on the Mental Scale and 102 on the Motor Scale. A third offspring had a neural tube defect complicated by hydrocephalus and died at 3 months. This mother had a family history of major congenital anomalies. We think that this experience supports the view that Hartnup disorder in the mother, unlike phenylketonuria, does not have an adverse effect on the fetus. The presence of normal ratios of the amino acid concentrations between maternal and umbilical veins in one mother also suggests that placental transport of free amino acids, unlike renal transport, may not be reduced in maternal Hartnup disorder.