Cardiovascular physiology of the human fetus

Efforts to develop a system for the diagnosis and treatment of heart disease in the fetus and neonate are dependent upon a fundamental understanding of the interaction between form and function of the fetal cardiovascular system. Recent advances in the field of molecular biology have suggested that single gene defects may be involved in the development of a larger proportion of congenital heart disease than was previously appreciated. Once organogenesis has been completed the architecture of the fetal cardiovascular system reflects the pressure and volume of blood flow through the developing chambers and blood vessels. Fundamental differences in cellular structure and arrangement of the myocardium and functional changes attending biochemical differences in contractile elements and their interaction with available cations impart alterations on mechanical function of the intact heart, and alter the response of the myocardium to alterations in structure and stress. In this review of cardiovascular physiology of the human fetus we attempt to review observations of regional blood flow distribution in the normal and abnormal fetal circulation. We rely upon two-dimensional echocardiographic imaging of cardiovascular structure and Doppler analysis of flow in the human fetus to draw conclusions regarding the normal and abnormal physiology and compare these findings to the fetal cardiovascular principles that have been previously defined in the lamb.