The effects of specific birth stressors on four indexes of lateral preference

Coren S, Searleman A, Porac C

1982

Canada

1,239 mothers indicated whether their offspring's' births had been associated with potential birth stressors (premature birth, prolonged labour, breathing difficulty, low birth weight, breech presentation, Rhesus incompatibility, instrument birth, cesarean birth, multiple birth). Data about the handedness of their offspring had been gathered. When the mothers reported that a birth was stressful or complicated there was an increased likelihood that the child would be left handed. The effect was much larger for males than for females. Other aspects of sidedness were affected by birth stress.

This is one of the most important studies of handedness from a primal health research perspective