A baby’s sleep cycle is very different from adults. An adult’s sleep cycle is typically around 90-120 mins, while that of a baby is 50 mins. Within this cycle, there are stages of wakefulness, light sleep, vivid dream sleep and deep sleep that occur continuously.
Adults spend 20% of their time in REM sleep (sleep in which we dream vividly), and 80% in NREM (stages of light sleep and deep sleep, where our body and mind relaxes. Babies spend equal amount of time in both REM and NREM sleep. Since the baby sleep cycles are shorter, along with equal periods of REM sleep, they wake up more.