A Norwegian researcher, Kjell Åmund Salvesen at St Olav’s Hospital in Trondheim, has through his studies come to the conclusion that ultrasound during pregnancy increases the chance of having a left-handed baby. It is especially true if the baby is a boy.

Salvesen’s study included almost 9000 children, all of whom were classified as either right- or left-handed. The result of the study is that a mother who has had more ultrasound during her pregnancy has a 15% increased chance of having a baby who is left-handed, compared to mothers who had no ultrasound. The chances were even greater for mothers who had ultrasound before they reached week 20 of their pregnancy. Famous left-handed men include: Paul McCartney, Leonardo da Vinci, and John McEnroe.

Leonardo da Vinci (1452-1519), above his self-portrait, was left-handed. But it seems he also used his right hand a lot.