Plasma protein levels in normal human fetuses: 13 to 41 weeks' gestation

OBJECTIVES: To establish reference ranges for the levels of alpha-fetoprotein, albumin, prealbumin (transthyretin) alpha-1-antitrypsin, transferrin, ceruloplasmin and total protein in the plasma of normal human fetuses and newborn babies. DESIGN: Prospective study of individual normal cases to fulfil objectives. SETTING: Pathology laboratories of the University of Edinburgh and the biochemistry laboratories of the University of Keele. SUBJECTS: Twenty-two normal fetuses 13 to 22 weeks of gestation and 66 babies born between 24 and 41 weeks gestation. RESULTS: Albumin is the predominant plasma protein throughout gestation. The levels of alpha-fetoprotein and prealbumin fell significantly with increasing gestation, whereas the concentrations of the other proteins studied increased. The ratios of individual proteins to total protein demonstrated similar trends. CONCLUSIONS: This study provides developmental profiles of normal human fetal plasma proteins to serve as possible reference data for abnormal fetuses. Declining levels of prealbumin (transthyretin) were unexpected and suggest a functional role for this protein in early pregnancy.