When the babies get older, their sleep needs become more similar. The gap of “normal” sleep narrows, with infants getting between 10.5 and 18.5 hours per 24-hour cycle. Bedtime for most babies will be late, around 9 or 10 p.m. But after baby goes to bed, there is a huge difference in sleep patterns. Some babies will continue to wake for a feed every three hours, while others will sleep through the night. Both are normal, but if your baby is waking every hour or two, you should try to encourage longer sleep patterns.
 
First, check with your doctor. There may be a medical condition, such as acid reflux, that’s causing her to wake during the night. Or your baby may not be able to lull herself back to sleep when the natural sleep cycles switch over. Adults have four stages of sleep, plus REM (rapid eye movement); infants only have two—active and quiet.

Infants enter sleep through the active stage, and alternate between active and quiet every 50 to 60 minutes. If you notice your child waking every hour or two, she’s likely waking up while switching in and out of active sleep and doesn’t have the ability to soothe herself back to sleep. A white noise machine that runs through the night may help ease her back to sleep on her own.