Dr. Greene's Answer
When poor sleep starts suddenly that way, often something has changed for the child. It might be pain, such as a new ear infection, or it might be a new phase, such as separation anxiety. Here are some thoughts on changes in sleeping through the night.
The most common symptom for ear infection is suddenly not being able to sleep. If you haven’t checked for that possibility, take her to the pediatrician to rule it out.
Molars could certainly make her uncomfortable and could have triggered this period. It would be okay to try some Motrin or Tylenol before bed to see if decreasing teething discomfort helps her to sleep.
Sometimes a new developmental phase can cause a change in sleep patterns as well. For example, if your child has recently learned to walk or if her language is really taking off, she might be more excited about practicing her new skills than sleeping through the night.
If kids are fine, one of the fastest ways to get them to sleep is to gently bend their hips down with one hand so they can’t get up and move about, and pat them or sing to them, staying with them until they drift off. Do anything except picking them up, feeding them, or lying down with them if you want to teach them to fall back asleep on their own.
Usually about four nights of this will teach kids that they can relax and they will drift back to sleep. Most of the time, this makes kids feel safer so they’re better able to tolerate your not being there later. Kids can get attached to almost anything, though, so there is a small chance they would get used to having you there. However, if she’s afraid you might leave at any moment, she may be too tense to relax and fall back asleep.
Kids at this age sleep on average 12 to 14 hours out of 24, and at this age some do better with one nap and some with two. When they are overtired they can sleep badly, too. However, kids tend to get the sleep that they need as long as they have the opportunity.