Single umbilical artery with caudal defects in human fetuses

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Abstract
Single umbilical artery associated with multiple anomalies is described in three stillborn human fetuses. Detailed study of the abdominopelvic arteries showed replacement of the abdominal aorta below the origin of the superior mesenteric artery by the umbilical artery in all three specimens. This finding greatly helps in solving the age‐old riddle of the cause‐effect relation between the umbilical anomaly and its associated defects. Single umbilical artery can give rise to the developmental anomalies in three ways. First by replacing the greater part of the abdominal aorta and disturbing the blood supply of the caudal half of the body during early embryogenesis it can give rise to the developmental anomalies of the cloaca, the genitourinary, gastrointestinal, and central nervous systems, and of the lower limbs; second by impairing the growth of the umbilical mesoderm it can disturb the formation of the infraumbilical portion of anterior abdominal wall and its correlates; and third by disturbing the hemodynamics of the embryo it can give rise to cardiovascular anomalies and possibly also to defects toward the cephalic half of the body. Although single umbilical artery and the associated developmental defects may both be secondary to another regionally operative teratogenic influence the extreme vascular reduction caudal to the aorticoumbilical junction and the concentration of malformations in the caudal half of the body greatly support the angiogenic theory.