According to a study is has nothing to do with strength, or being right or left-handed, and possibly everything to do with evolution.
The study published in the journal Nature Ecology and Evolution found 70 – 80 per cent of women who carry their baby on their left side, also known as left-cradling bias, do as a way to keep their baby safe.
The study says this favouring “potentially facilitates mother–infant relationships” and “arises from the right hemisphere advantage for social processing, for example, visual recognition of infant facial expressions.”
They add: “The position of an infant on the mother's left side may optimise maternal monitoring, by directing sensory information predominantly to the mother's right hemisphere."
In short, the right side of the brain is linked with the left side of the body and is responsible for interpreting emotional signals. So, by holding your baby on the left side of your body, you're are able to better connect with your child.
The bias doesn’t just occur in women. Little girls also tend to hold dolls of their left side too.
Interestingly, the study says fathers do tend to hold a baby on the left, however, the research found men without children do not favour a side.
This article first published on Practical Parenting.