How long does the average newborn sleep? When do newborns start having a proper sleep pattern and why do newborn sleep patterns differ from adults?

New born sleep is erratic and unpredictable. Every baby is different. Most newborn babies don't stay asleep for more than two to four hours at a time, day or night, during the first few weeks of life. Newborns typically sleep 14 to 18 hours a day in the first week and 12 to 16 hours by the time they're a month old. Babies wake often because their sleep cycles are shorter than adults. After about an hour of deep sleep baby will reenter the light sleep stage. During this period any kind of stimulus can awaken baby. Baby will enter this period of sleep every hour or so throughout the night. Most restless nights will occur because baby has trouble getting back to the stage of deep sleep, not because they can’t stay asleep. http://www.askdrsears.com/topics/health-concerns/sleep-problems/infant-sleep-patterns