What's Normal?

Does your baby seem behind in his developmental milestones? Relax. These markers are more arbitrary than you might think.

baby wearing a white onesie crawling GettyImages.com

When he's a month old or so, your baby is going to return your smile. And you are just going to melt. Then, before you know it, he'll begin to coo like a dove and clutch objects with his chubby little fingers. He'll roll over from his back to his tummy, and soon he'll be sitting up on his own. Every time he masters one of these developmental milestones, you'll marvel at his accomplishment, run for the video camera and boldly announce his progress to various friends and family.

Thrills aside, milestones help you gauge how your baby is developing. Especially if this is your first child, you'll probably pore over baby books to learn what tricks he will perform next, then await them in anticipation. But there's a flip side to milestones: If your baby doesn't hit one on schedule, you could suffer unnecessary anxiety.

"Milestones are great to look forward to. They're rewarding and are a way of getting your goodies as a parent," says Barry Lester, Ph.D., director of the Infant Development Center at Women & Infants Hospital in Providence, R.I. "But I think that milestones are also overrated," he adds. "People worry about them way too much and take them way too seriously."

The worry can start early. For Connie Dempster, 35, of Brooklyn, N.Y., it began when her baby, Emma, was just 3 months old. The baby next door, who was about the same age, was very vocal—babbling, squealing and jabbering away—while Emma hardly made a peep other than to cry or otherwise complain. Dempster was panicked. "I told my husband, 'We're not talking to her enough, we're not stimulating her, we have to buy audiotapes,'" she recalls. "I was worried that she might be deaf. I wanted her to get a hearing test." Although Dempster understood intellectually that there's no problem unless a baby is significantly late in reaching a milestone (which Emma wasn't), that didn't stop her from worrying.

What's 'Normal,' What Isn't ?

What's normal is much more variable than most parents realize. That's because we tend to read and hear about averages, which are based on all kinds of babies: big and little, early and late, first and last, and all those in the middle. "But the books don't tell parents what normal ranges are," Lester says. For instance, on average, babies walk at age 11 or 12 months, but the normal range is anywhere from 8 to 15 months.

What accounts for the variability? "Everything you can think of can affect a baby's development," Lester says. Genetics and personality certainly predispose babies to develop slower or faster, but other factors also can be influential. For instance, big, chubby babies typically are slower to master physical milestones, such as rolling over or sitting up, because they have more body mass to move. Babies with older siblings may develop faster because of the extra stimulation they receive. A baby who grows up in a bilingual home may develop certain language skills more slowly. And some babies who are premature or underweight at birth take longer to master motor tasks, such as rolling over, although most eventually catch up.

A baby's sleep position also can affect his development. One study found that babies who are placed to sleep on their backs (which is strongly advised to help prevent sudden infant death syndrome, or SIDS) crawl later than those who sleep on their tummies: at 8 1/2 months on average, compared with 7 1/2 to 8 months. However, crawling may be a questionable milestone, according to Beth Ellen Davis, M.D., M.P.H., a pediatric-development specialist at Madigan Army Medical Center in Tacoma, Wash. Some researchers have theorized that infants who skip the crawling stage altogether have reading problems, such as dyslexia, later.

But, Davis says, "There are no evidence-based studies associating crawling with reading."

This point about crawling underscores the fact that you shouldn't worry about one specific milestone. If your baby is mastering most of them at an appropriate age but is slow to acquire a particular skill, don't be concerned. That said, most babies do slow down or even stop development in one area, such as language, while they're mastering skills in another—motor development, for example. "An advance in one system can come at the cost of a regression or standstill in another," Lester explains.

There are a few red flags, however. Among them are a failure to make consonant sounds, like "ma," "da" or "ba," by 8 months or to walk unassisted by 16 months. And by age 1, a baby should be speaking at least two or three real words, like "bye-bye" or "mama," and should be interacting socially, says Ellen Perrin, M.D., professor of developmental-behavioral pediatrics at the Floating Hospital for Children at Tufts-New England Medical Center in Boston.

Is faster smarter?

For many parents, it's not fear that prevails, but pride. While you may declare your baby a genius or a future Olympian if he masters his milestones early, as long as he's within the normal range, there is no correlation between how far ahead of the pack he is now and how successful he will be later. However, a child who reaches several milestones late, outside of the normal range, is more likely to have problems, Lester says.

Still, experts say there's no good reason to push a baby to meet his milestones early. Nor is there any evidence that parents can speed things along, anyway. "A milestone is, by definition, something that just happens," Lester says. "A lot of what goes on is programmed, and I don't think you can do anything to make it happen faster." There's one known exception: If your baby sleeps on his back and you want to encourage him to crawl, place him on his tummy for at least 15 to 30 minutes of supervised playtime every day.

In addition, you certainly can encourage a child's development by providing a stimulating environment. For instance, talking and reading to your baby may not make him speak earlier, but it may make him more vocal and give him a broader vocabulary when he does begin to talk. "I don't think expensive developmental gimmicks are worth the money," Perrin says, "but I do think it's very useful to read and talk to a child and imitate her sounds. Doing so also teaches the value of reading and social communication."

Likewise, you can help your baby achieve a new skill when you see he is ready to go for it. Prop him up against pillows when he shows that he likes to sit up, give him more opportunities to stand when he begins doing that, mimic or answer him when he starts to babble. If nothing else, doing this is great for your relationship with your child. "The message," Lester says, "is to relax and have a good time together."