About two-thirds of newborns are born in the left vertex position during the last 3 to 4 weeks of a full term pregnancy, with the most common ones being left anterior occiput (LOA) or transverse (LOT). The 2:1 ratio between left and right vertex presentations complies with that for left and right head position preferences in newborns, which in turn has been linked to the acquisition for hand preference.
See Brain (or encephalon), Delivery position (presentation), Diarthrodial joints, Handedness, Newborn, Pelvis/pelvic girdle, Sexually dimorphic