My 4-month old sleeps at 10pm and wakes up at 7am. Is 9 hours of sleep enough for her age?

My baby is 4 months old and she also sleeps around 10pm and wakes up around 6 or 7am. 4 month olds can go up to 8 hours without milk. They also nap frequently in the day. An average is 3 naps a day, amounting to about 4 to 5 hours. Don't be too worried as babies will fall asleep when they are tired. You just need to ensure that they have a cosy environment for sleeping in. http://www.parents.com/baby/sleep/basics/understanding-baby-sleep-4-6-months/#page=1