ABSTRACT
The decline in the urinary urea to ammonia ratio represents a simple measure of nutritional
status in the adult. We examined the relationship of this ratio to nutrient-related
fetal growth retardation. Levels of ammonia and urea nitrogen were measured in the
first voided urine and cord blood from 15 term infants exhibiting a wide range of
growth. Analysis by multiple regression with neonatal ponderal index as the primary
dependent variable revealed a significant correlation between lowered ponderal index
and decreased urinary urea and ammonia. The correlation was primarily a function of
increasing ammonia levels, with no relationship between fetal leanness and urinary
urea. Comparable cord artery and vein ammonia suggest that placental ammoniagenesis
was not a major determinant of observed elevations in urinary ammonia. Confirmation
of the striking correlation between increased urinary ammonia and lowered neonatal
ponderal index may afford a simple test for the identification of nutrient-related
growth retardation.
