The back-sleeping babies are all right.

Twenty years ago, alarmed by the number of babies dying from sudden infant death syndrome, doctors began telling parents to place sleeping babies on their backs.

While the “Back to Sleep” campaign cut the SIDS rate in half, it provoked a new worry: Were back-sleeping babies able to roll over properly?

The answer, according to a new study, is yes.

A Canadian research team examined the motor skills of more than 700 infants and then compared their motor skills with those of babies studied in the 1990s. The researchers found that 90 percent of the infants developed rolling skills at roughly the same age as babies studied 20 years ago.

In connection with the Back to Sleep campaign, doctors encouraged parents to give babies a little “tummy time” — placing infants on their bellies while awake to help build upper-body strength and healthy motor skills.

The practice is common, although some media reports have questioned its necessity based on the recent study.

Dr. Richard Velders, a pediatrician at Hennepin County Medical Center, recommends tummy time. He said he did not see any connection between the study’s findings on rolling-over ability and tummy time.

“There are plenty of studies that show that babies’ development is helped by tummy time,” he said. “This study isn’t saying that tummy time is detrimental or unnecessary to human development. It’s not saying tummy time is bad or good for babies.”

The benefits, he said, are plentiful and begin right from birth. “This is baby’s exercise,” he said. Just don’t leave the baby alone.

“When you do tummy time with a baby, you don’t just plop them on their tummy and go cook breakfast,” he said. “You put a toy in front of them and you talk to them. That’s how you promote development in babies.” □