Q: Dear Mr. Dad: My sister and I have toddler girls who are only a week apart. Hers started walking at about 9 months, but at 16 months mine still hasn't taken a step. Our pediatrician isn't worried and I know I shouldn't compare my baby to anyone else's, but it's hard not to. Is there anything I can do encourage my baby to walk?

A: No. On average, babies take their first steps at about 12 months. But, the range is pretty big, from 9 to 18 months. How early -- or late -- a child starts to walk depends on a number of factors:

- Genetics. If you and/or your partner were early or late walkers, chances are your child will be too.

- Birth circumstances. If your baby was born prematurely, she'll probably be a late walker. Researchers have found that very low-birthweight, preterm infants learn to walk at an adjusted age of 14 months (meaning their actual age plus the number of months they were born early). Premature babies usually catch up to their agemates by the time they're three, but the more premature the baby, the longer it takes to pull even.

- Older siblings. Having a brother or sister who's a few years older sometimes gives babies a little extra incentive to walk early.

- Medical issues. Your baby may learn to walk late if she had to go through a lot of medical intervention early in life, or if she simply got sick or had a bad fall right when she was about to take her first steps.

- Scheduling issues. Your baby has a lot going on now, including learning to speak, trying to identify everything in sight, and establishing her independence. And she may simply have decided that walking isn’t that much of a priority -- especially if she's a fast crawler.

- Environmental factors. Slippery floors, bulky clothing, and parents who gasp every time the baby looks like she's going to fall, can contribute to delays in walking.

The whole crawling-to-walking transition is full of myths. You may hear, for example, that babies who scoot or slide or roll instead of crawling develop behavior problems later in life, presumably because they missed a major developmental milestone. Or you might hear that early walking is a sure sign of genius in the making. Or you might hear the opposite, that early walkers do poorly in math and science because crawling helps develop the brain. None of it's true.

Bottom line? Your baby will learn to walk when she's good and ready and there's nothing you can -- or should -- do to change her schedule.