Here’s a picture of me doing my fencing pose during my first month:
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It’s actually a normal finding in newborns. According to Wikipeidia (and no, Mommy doesn’t go there for medical information routinely, but it’s good for layman’s definition):
The asymmetrical tonic neck reflex (ATNR) is a primitive reflex found in newborn humans, but normally vanishes by the child’s first birthday. It is also known as the “fencing reflex” because of the characteristic position of the infant’s arms and head, which resembles that of a classically trained fencer. When the face is turned to one side, the arm and leg on the side to which the face is turned extend and the arm and leg on the opposite side bend.
There are plenty of other reflexes such as the sucking, Moro and Babinski which require video capture to better show the reflex, but I have exhibited them all!