It is common for babies who have slept through the night until now, to begin waking up at night. Reasons for this might be the baby wants to play; he might not feel well, he may be teething, he may be hungry or wet, or it may just be the development of a new sleep cycle and behavior. Unless your baby is in pain, it is best for your baby to try to learn to comfort himself to get back to sleep. Leave him alone for a few minutes to see if this happens. If it doesn’t, comfort your baby and tell him it’s time to go to sleep. He may cry a little and this is OK. If your baby cries for more than 15 minutes, or begins to cry uncontrollably, go back in to comfort him. You may also find that you need to move baby's afternoon nap up 30 minutes or wake him from this nap earlier to enable him to get tired enough before bedtime to sleep through the night. Keep in mind that your baby is growing and developing and often this will result in changes in sleep patterns. If you have not already done so, you may want to develop a bedtime routine that will assist your baby in preparing for a good night's sleep. This might include a feeding, a warm bath, a massage, a good book or story and some soft music. The process of developing good sleep habits can sometimes be trial and error so work with your baby's normal routine to come up with something that works for you and baby together.