Is this developmental milestone falling out of favor?

Q: My son is 9 months old and he's still not crawling. Should I be worried?

A: Late or never crawling is common among babies today and is being attributed to the rise in back sleep, the sleep position recommended by the American Academy of Pediatrics to reduce the risk of Sudden Infant Death Syndrome (SIDS). Back sleep has caught on so well that many parents never put babies down on their stomach, even during waking hours. As a result, crawling, which used to start at 6 to 8 months of age, is falling out of favor as a developmental milestone. Beth Ellen Davis, M.D., a developmental pediatrician at the Madigan Army Medical Center in Tacoma, WA, led a study showing that kids who never crawl end up walking independently at the same time as crawlers. Daily tummy time, when he's awake, can help to encourage crawling.