i copied this from the following website:
http://kidshealth.org/PageManager.js...icle_set=10233
The First 6 Months
There is no sleep formula for newborns because their internal clocks aren't fully developed yet. They generally sleep or drowse for 16 to 20 hours a day, divided about equally between night and day.
Newborns should be awakened every 3 to 4 hours until their weight gain is established, which typically happens within the first couple of weeks. After that, it's OK if a baby sleeps for longer periods of time. But don't get your slumber hopes up just yet — most infants won't snooze for extended periods of time because they get hungry.
Newborns' longest sleep periods are generally 4 or 5 hours — this is about how long their small bellies can go between feedings. If newborns do sleep for a while, they will likely be extra hungry during the day and may want to nurse or get the bottle more frequently.
Just when parents feel that sleeping through the night seems like a far-off dream, their baby's sleep time usually begins to shift toward night. At 3 months, a baby averages 5 hours of sleep during the day and 10 hours at night, usually with an interruption or two. About 90% of babies this age sleep through the night, meaning 6 to 8 hours in a row.
But it's important to recognize that babies aren't always awake when they sound like they are; they can cry and make all sorts of other noises during light sleep. Even if they do wake up in the night, they may only be awake for a few minutes before falling asleep again on their own. It's best if babies learn early to get themselves to sleep, so let your baby try.
If a baby under 6 months old continues to cry for several minutes, it's time to respond. Your baby may be genuinely uncomfortable: hungry, wet, cold, or even sick. But routine nighttime awakenings for changing and feeding should be as quick and quiet as possible. Don't provide any unnecessary stimulation, such as talking, playing, or turning on the lights. Encourage the idea that nighttime is for sleeping. You have to teach this because your baby doesn't care what time it is as long as his or her needs are met.
Ideally, your baby should be placed in the crib before falling asleep. And it's not too early to establish a simple bedtime routine. Any soothing activities, performed consistently and in the same order each night, can make up the routine. Your baby will associate these with sleeping, and they'll help him or her wind down. You want your child to fall asleep independently, and a routine encourages babies to go back to sleep if they should wake up in the middle of the night.