BIOCHEMISTRY OF AMNIOTIC-FLUID WITH POOR FETAL GROWTH

Amniotic fluid from 79 European and Asian mothers at term was examined for those biochemical changes which in postnatal life are associated with slow growth, a poor diet or frank malnutrition. Amniotic fluid from normal pregnancies of both races contained proportionally less urea nitrogen, more uric acid nitrogen and α‐amino nitrogen, and more free hydroxyproline than was found in urine from pregnant mothers and the newborn. Some of these differences may reflect a relative reduction in nutrient supply in late pregnancy while others are due to immaturity of various biochemical systems. These explanations do not account for all the differences. Compared to results in normal mothers, the Asian mothers with light‐for‐dates babies showed changes suggesting undernutrition (high amniotic fluid alkaline ribonuclease and ‐amino nitrogen). The European mothers with light‐for‐dates babies had biochemical evidence of reduced growth (low amniotic fluid total hydro‐xyproline) but not evidence of undernutrition. Mothers with light‐for‐dates babies in both races had a high amniotic fluid uric acid nitrogen; the cause of this is uncertain. The biochemical measurements were significantly different in the mothers with light‐for‐dates babies and were a more accurate prediction of poor intrauterine growth than clinical criteria alone. Nevertheless, the overlap with normal pregnancies was so great as to limit the clinical usefulness of these measurements in the management of an individual pregnancy. Copyright © 1979, Wiley Blackwell. All rights reserved