Right after birth, when Lucy hears a loud noise, when you change her diaper, when you pick her up—in short, any time you disturb her—she shakes her arms and legs while extending her limbs in a wide motion that lasts a few seconds. Scientists believe that this is an archaic reflex dating back to our monkey ancestors and that it helped babies hang on as their mommies hopped from tree to tree. The Moro reflex, as it is called, is strong at birth, fades rapidly in the first few months, and persists as a fine trembling of the hands even at six months. Lucy may develop another very cute little motion around eight months called hand flapping. When she’s upset or scared she’ll flap her fingers just as a flamenco dancer would click her castanets. This won’t last too long, and you’ll miss seeing it when she stops.
In Older Children
A slight shaking of the fingers is normal in kids of all ages. Ordinarily, the cause is hunger or, more precisely, low blood sugar caused by hunger. Beyond that, some children display a slight shaking of the fingers that comes and goes and has no clinical significance.