Asymmetry of the left-right (L-R) axis is a feature of vertebrates that is apparent in the viscera and vas­cu­lature. An understanding of L-R patterning in human development is aided by familiarity with key events and important pathways in mammalian embryogenesis.The induction of L-R asymmetry follows the establishment of the anteroposterior (A-P or rostrocaudal) and dorsoventral (D-V) axes and re­quires the pre-existing midline symmetry to be broken before sidedness is induced via a series of comp­lex, coordinated molecular signaling events. In this review, our aim is to describe the molecular back­ground of this embryological process, and give brief knowledge concerning its clinical con­se­quences.

(Gynecol Obstet Reprod Med 2006; 12:000-000)

Key Words: Heterotaxy, Laterality, Situs anomalies