The development of hemostasis in the human fetus and newborn infant

Fragmentary understanding of normal perinatal hemostasis limits the clinician in his evaluation and therapy of neonatal hemorrhage. This report attempts to outline current concepts of hemostasis and to summarize the data obtained from fetal and perinatal studies, including investigations by the authors on human embryos and fetuses. The developmental events in human hemostasis are described and normal values for vascular, platelet, and clotting factor determinations are tabulated. Ontogenetically, the sequential development of vessel contractibility, platelet aggregation, and fibrin formation appears to recapitulate the phylogenetic pattern.