Physical Development

Your pediatrician will want to schedule a six-month checkup around this time, including a third round of vaccines (generally polio, DTP, and hepatitis B). After checking baby's height, weight, and head circumference, she'll compare the results with those from previous visits to be sure your baby is following a normal growth curve. You'll also learn the percentile your child is in--how his height, weight, and head size compare with those of other babies his age. However, it's important to remember that the curve, not the percentile, is the best indicator of healthy development. A baby who consistently measures, say, in the 20th percentile for weight--meaning that 80 percent of babies are heavier than he is at this age--is much more likely to be thriving than one who starts out in the 90th percentile and drops to the 40th. So resist the urge to compare your baby's development with that of other babies, and ask well-meaning relatives to do the same.

Social Development

Some babies see bath time as a nightly party, while others scream at the sight of running water. Both of these feelings may be exacerbated by a switch from the baby bath to the big tub, which generally happens around now. If your little one fears the tub, don't force him to use it--continue using the baby bath, or give him sponge baths if he resists being submerged. You can also try joining him in a group bath (just make sure the temperature is right for him, which may make it a little cool for you). One tip: Never let the water out while baby is sitting in the tub. Not only will the gurgling sound scare him, but older babies may see the water running out and fear that they're about to be washed away.

Intellectual Development

Without meaning to, parents may actually impede their child's learning process because "he isn't doing it right." For instance, if baby chews his new plastic rings instead of arranging them by color and size, you may want to show him the "correct" way. Resist the impulse! Instead, let him direct the play. If chewing is the order of the day, let him try a variety of (safe) objects to compare textures and tastes. If he'd rather bang, pull out the pots and pans and start a baby band. He'll get the message that learning is fun, and he'll be more amenable to your play ideas once he knows that you support his.

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.