9 weeks old

BREAK OUT THE BIBS
Your baby's salivary glands have been working since she was in utero, but you may notice that she's started to drool. She's also putting everything in her mouth and producing more saliva than she can swallow.

This doesn't mean that your baby's teething just yet, though — that probably won't happen for another two weeks, at least. The vast majority of babies sprout their first tooth between 4 and 7 months of age. If your baby's an early developer, you may see her first white cap, usually one of the bottom two middle teeth, as early as 3 months. (And in rare cases, a baby's first tooth is visible at birth!)

Many parents permanently affix a bib to their baby about now to catch the drool. Just remember to take it off when your baby sleeps to prevent strangulation.

The good news is that your baby's drool coats toys and other objects with disease-preventing proteins. That's fortunate — since she'll continue to explore anything she can get her hands on.

SLEEPING FOR A LONGER CHUNKS OF TIME
If your baby's sleeping through the night (five or six hours at a stretch), you're one of the lucky few. Most 10-week-old babies still wake up in the middle of the night. But even babies who aren't sleeping through the night at this stage should be sleeping and staying awake for longer intervals instead of cycling back and forth so much. Your baby will most likely have two to four long sleep periods and as many as ten hours of awake time in 24 hours.

An interesting note: Whether your baby is a night owl or a morning lark, a long sleeper or short sleeper, she'll probably stay that way throughout childhood.

TURNING OVER A NEW LEAF
Your baby is learning how to rock and roll — well, maybe just roll. At this age, she'll probably be able to move from her side to her back and her back to her side. The complete roll over won't come for another month or so, though, because she needs stronger neck and arm muscles for that maneuver.

Your baby's increasing mobility means that you must keep a hand on her during diaper changes. Never leave your baby unattended on a bed or any other elevated surface now that she can move around.