Eighty fetuses referred because of maternal alloimmunization or maternal infection underwent umbilical venipuncture and were found to be unaffected. Norms for hematologic, biochemical, and pressure measurements were constructed from 18 weeks until term. Total red blood cell (RBC) count (P <.0001), hemoglobin (P <.0001), white blood cell count (P <.0001), and platelet count (P=.04) and volume (P <.03) each rose with advancing gestation. The number of nucleated RBCs declined significantly (P <.0001). Umbilical vein carbon dioxide pressure rose (P <.009) and oxygen pressure declined (P=.005) with advancing gestation. Total protein and albumen rose (each P <.0001). Aspartate aminotransferase (P <.02), alanine transferase (P <.0001), and gamma-glutamyl transpeptidase (P <.0001) each rose with gestation, independent of any other measured value. The rise in lactic dehydrogenase with gestation was found to depend on pH (P=.0002) rather than gestational length. Paired maternal-fetal serum samples were obtained from an additional 50 abnormal fetuses; there was no significant relationship between mother and fetus for the concentrations of any of the studied enzymes. Umbilical vein pressure rose progressively with gestational age (P < .004). These studies reveal new information on fetal development and provide a baseline from which to evaluate either fetal disease or the response to therapy.
(C) 1992 The American College of Obstetricians and Gynecologists