4fb89720_nd_solving_baby_sleep_problems__What_to_try
[Problem] "My nine -- month -- old was sleeping through the night, but now he's started waking up again." [What to try] 
You're not going back to square one when it comes to sleep, even if it feels that way. This is just a temporary blip on the road to sleep nirvana. Chances are your baby is experiencing one of the following two common scenarios. A developmental breakthrough. If she's learning to pull herself up to a standing position, for example, she may feel "driven" to practice that new standing up skill at 3 am -- only to discover that she can't get herself back into a seated or lying down position. Separation anxiety. Keep your baby close to you during his waking hours. Remember separation anxiety is the ultimate compliment to you: you're special!
From A to ZZZZs: The quick guide to preventing and solving baby sleep problems
What to try