Some aspects of fetal biology.

Fetal blood sampling under ultrasound control is rapidly expanding the study of human fetal biology. Pure fetal blood is required for prenatal diagnosis, establishment of reference ranges for biologic measurements and assessment of fetal welfare. Hematological, biochemical and immunological parameters were selected on blood of normal fetuses sampled between the 18th and 36th week of gestation. They were referred to us for various prenatal diagnosis (mainly toxoplasmosis) but were well and confirmed healthy at birth. These data indicate a slower metabolism in fetuses compared to their mother, a lower level of energy requirement and a relative liver immaturity. An important point concerns the evolution of some parameters all along the pregnancy. The correlation observed between the different biological levels either in cord or maternal sera (or between both) paves the way for future studies concerning fetal metabolism. These normal values of fetal biology will improve our knowledge of physiology and help to determine the specific values of a test in fetal pathology.