Prenatal ultrasound scans thought to be the safest of imaging techniques may be powerful enough to affect the brain in utero, researchers surmise.
Even one or two scans could be enough to switch cerebral dominance, resulting in less right handedness in children.
Analysing several recent studies, Nigel Paneth from Michigan State University said that definitive proof is hard to come by. The studies do not state that there is an excess of left handedness in scanned children, but that there is an excess of non right handedness, which suggests some children are ambidextrous.
The actual excess of left handed children is around 12 per cent, which he feels is not significant, whereas the number of ambidextrous children was important (Lancet, 1998; 352: 5-6).