The human fetal venous system: normal embryologic, anatomic, and physiologic characteristics and developmental abnormalities.

OBJECTIVE The introduction of high-resolution ultrasonography combined with color-coded Doppler imaging offered a breakthrough in the evaluation of the human fetal venous system, considerably enhancing our understanding of fetal venous circulation in normal physiologic conditions, as well as providing us the ability to study circulatory changes in abnormal circumstances. The purpose of this study was to describe the normal anatomic development and complex of anomalies of the human fetal venous system and to review recently published series of these anomalies. METHODS Normal embryologic and anatomic development is described. An English language literature search of recent MEDLINE listings was performed to glean data from recently published series reporting prenatal diagnosis of the various anomalies and their associated malformations. RESULTS Anomalies of the human fetal venous system occur sporadically, often associated with cardiac or other malformations. The pathophysiologic mechanisms leading to abnormal in utero development of the human venous system remain largely undetermined. On the basis of the type of vein involved, embryologic precursor, and etiologic correlation (primary or secondary), classification into 4 major groups is described. CONCLUSIONS Prenatal evaluation of fetuses found to have anomalies of the venous system should include a careful search for cardiac anomalies, including pulmonary venous drainage, and a detailed anatomic survey of the umbilical, portal, hepatic, and ductal systems to determine aberrant communication and, if possible, to discover clues to systemic diseases or thromboembolic phenomena.