Q. My baby was sleeping through the night, but all of a sudden, at 8 months, she's waking up and crying. Why the change?
A. Does she have a fever or other symptoms of illness, such as coughing, poor appetite, diarrhea, or pulling on her ears? This can certainly wake up babies, so ask the doctor about it. Teething can disrupt sleep, too -- so take a good look at her gums, or feel them (watch out for biting!) to see if a tooth is coming through. If it is, a dose of acetaminophen at night -- check with your doctor for the right amount to give -- may let everyone sleep better.
But if she's healthy and not teething, the most likely explanation is separation anxiety. Before 6 to 8 months, when a person is out of sight, as far as a baby's concerned, she's out of mind. But suddenly, she realizes that people still exist even when she can't see them -- and she can get upset and overly clingy (day or night) when someone she wants, namely you, isn't in view.
I wish I could tell you that separation anxiety is a quick phase, but, unfortunately, it's not. It peaks at around 18 months, then decreases and usually disappears by age 2. At that point, kids understand that people can be gone from their sight, yet will still come back.
What your baby needs to know in the meantime is that you're nearby if she needs you. Reassuring her when she wakes at night by giving her a kiss, or singing a verse of a lullaby can help (keep in mind that any routine you start should be one you're willing to continue for a while!). Each one of my children has needed something different: Michaela loved lullabies, Zack wanted his back patted, and for Elsa and Natasha, nursing did the trick. Some families keep a lovey -- a favorite blanket or soft toy, maybe scented with a little of Mom's perfume -- nearby to help their children through this time.