Relation of glucose to alpha-fetoprotein in amniotic fluid.

A direct relationship between amniotic fluid glucose and alpha-fetoprotein (AFP) has been found between the 16th and 22nd weeks of pregnancy. This relationship is statistically significant (P less than .001) in each of the 6 gestational weeks tested, the coefficients of correlation vary from .74 to .91. The relationship between amniotic fluid AFP and another metabolite, urea nitrogen, was not significant (r = -.34), suggesting that the AFP-glucose relationship was not spurious. Absence of pregnancy-associated macroglobulins in the samples indicates that they were not contaminated by maternal serum. These data reflect an aspect of fetal metabolism or transport that should be investigated more thoroughly.