For example, when an adult sleeps, her sleep patterns are defined by short sleep cycles that last about 90 - 100 minutes. (parentingscience.com)
Babies have significantly shorter sleep cycles than adults, meaning they move into a light sleep mode more often, which gives them opportunities to wake up. (swanling.com)
However, babies are notoriously light sleepers with short sleep cycles — and are more socially aware every day — so they'll stir at the slightest whisper, smartphone - screen flicker, even your scent as you walk into the room. (parents.com)