Saucers, whose sales shot to $30.5 million last year, are essentially walkers without wheels. In 1992, the AMA unsuccessfully sought to ban walkers, primarily because kids could tumble down stairs in them. With saucers, “you’ve gone from the most dangerous thing that people used to buy children” to a safer device, says Portland, Ore., pediatrician Robert A. Mendelson, who uses saucers in his waiting room. But walkers turned out to have other problems, too: studies showed that they hinder some children’s walking skills and hurt their muscular and spinal development. Now some experts worry that the stationary play center, which hasn’t yet been studied as thoroughly as walkers, may have the same drawbacks. “It sets up incorrect postural alignments,” says Chicago’s Mary Week of Children’s Memorial Hospital, which recently worked on a pilot study of saucers. Because saucers put very small kids upright before their muscles are ready, she says, “babies hyperextend their backs and they drop their stomachs out forward, and they end up with sway-back.” When she treats teenagers suffering from back pain, Week says, she always asks what gear they had when they were very small. One response is almost unanimous: walkers.

The critics argue that children learn more when they’re unfettered, because then they can test both their environment and their motor skills. Walkers and saucers, while freeing parents, limit kids. “It’s a selfish prop,” says Peter Gorski, director of developmental research at Massachusetts General Hospital in Boston. “Children learn very actively, so inhibiting their activity to some extent inhibits their learning abilities.” Small kids need supervised “tummy time” to develop back, neck, abdominal and buttock muscles. For this, a good, clean floor works just fine. It’s cheap, it’s safe and you can get down there with them.