Physical Development

Your child's teeth began to form during the early months of your pregnancy, but the first little chopper doesn't poke its way out until around the fifth or sixth month of life. This is not a development to set your watch by--some babies get their first tooth at 4 months, others at nearly a year. In most cases, the first two teeth to arrive are the lower central incisors, followed by four upper incisors and then, at around a year, the lower first molars. Keep them clean from the beginning by wiping them with gauze or using a baby toothbrush (no toothpaste yet, though).

Whenever the first teeth arrive, it's likely that they will be preceded by one to three months of teething. Symptoms include drooling, an occasional cough caused by excessive saliva, chin rash (saliva again), inflammation of the gums (mostly with first teeth), and discomfort while feeding. Your baby will want to chew everything she can get her mouth on, so be sure to have safe and soothing toys on hand: a chilled rubber teething ring, an ice cube wrapped in a damp dishcloth. Although some child-care books recommend them, avoid hard foods like raw apples, carrots, and celery sticks until baby is at least 10 months old. She could easily choke on them.

Social Development

Stranger anxiety starts to manifest itself between the fifth and seventh months, peaking a month or two later and starting to recede at about a year. It's caused by a variety of factors, including your little one's increased closeness to family members (she realizes that some people are more familiar, and therefore more comforting, than others), and her new ability to physically distance herself from you by rolling or crawling away. For the first time, she understands that you and she are two separate entities, and the realization frightens her. She responds by growing more attached to you than ever.

Although stranger anxiety can be hurtful to baby's admirers, especially grandparents and other adult family members, it generally passes. (Interestingly, babies tend to respond more positively to children, even children they don't know.) Allow your child to observe newcomers from the safety of your arms. Eventually, her curiosity will get the better of her, and she'll start eyeing the new person, even trying out a tentative smile. From here, she'll grow progressively more comfortable, until the newcomer is admitted to the circle of intimates--at least for now.

Intellectual Development

The realization that she is a separate person is one of the most important concepts your baby will grasp this year. Of course, she is distinct not only from you, but from all people and objects she encounters. This means that she can bang a toy on a table in order to hear the noise or get your attention. The "cause" (banging) creates an "effect" (noise and the sudden appearance of mommy). Don't be surprised if she needs to test this theory a dozen times a day. Make sure she has appropriate objects for her experiments (a wooden block is better for banging than a dinner plate, for instance), and encourage her to test her findings.

Note: The information above offers general guidelines, but all babies develop differently, and few hit their milestones precisely when the conventional wisdom says they should. If your child was born prematurely, you may want to use your due date as a baseline for following baby's development.