The introduction of this article makes reference to a couple of papers (e.g. https://doi.org/10.1038/s41598-017-16827-y ) that handedness is observable in utero but cautions small sample sizes for these studies.

Right, my question was more meant for how well established that is. And if it is open to influence. My searches made it look like it was not positive that handedness was fixed until a bit later. Still before formal schooling, but not necessarily in babies.

> We aren't in emergency service or work in an environment where lives are on the line.

Obviously these jobs have occasional acute long work times but I'd say that jobs where lives are on the line is precisely where society doesn't want chronically sleep deprived workers.