Complex sentence: The condition lasts from 30 seconds to 20 minutes and then fades, it may recur when the infant is placed on his or her side, as the intensity of color has been shown to be gravity dependent and considerably variable from one infant to another.
Split into simpler sentences: The condition lasts from 30 seconds to 20 minutes and then fades. It may recur when the infant is placed on his or her side, as the intensity of color has been shown to be gravity dependent and considerably variable from one infant to another.