The nation’s largest organization of pediatricians is telling its members and parents that children riding in cars should remain in rear-facing child safety seats until at least their second birthday, and preferably even longer.

That conflicts with advice given to parents for years by many pediatricians: that children’s car seats should be turned around shortly after their first birthday.

The new policy from the American Academy of Pediatrics, published Monday in the Pediatrics medical journal, is buoyed by research that shows children younger than 2 are 75 percent less likely to die or be severely injured in a crash if they are in a rear-facing child restraint.

Equally important, the academy now recommends that children remain in a seat with a five-point safety harness as long as possible, and should only transition to a booster seat that relies on the car’s adult seat belts when children exceed the height and weight limit for the five-point harness.

Five-point harnesses, which run across children’s shoulders and hips and buckle between their legs, provide more protection than a car’s seat belts because they distribute the crash forces evenly over the strong, bony parts of a child’s body.

The pediatricians also recommend that children remain in booster seats until they are 4 feet 9 inches tall, a height most kids don’t reach until they are between 8 and 12 years old.

Some of the recommendations will likely be met with scowls from elementary school children, who often want to stop using their booster seats as they get older, and from parents. Parents often welcome moving their children into a forward-facing position because their legs are getting longer and it gives the parent a better view of the child in the back seat while driving.

The central point of the report is that at every transition — from a rear-facing harnessed seat to a forward-facing harnessed seat to a belt-positioning booster — children lose some protection. So the pediatricians recommend that kids remain in each stage for as long as their car seats allow.

Even when kids are tall enough to solely use adult seat belts, the academy’s policy is that they should remain in the back seat until age 13.

“Every parent wants their kids to achieve things as fast as they can,” said Dr. Ben Hoffman, a University of New Mexico associate professor of pediatrics who helped write the new policy. “That’s fantastic for developmental milestones or for school. But for child passenger safety, that’s the wrong attitude to have.”

Next Monday, the federal government is set to issue its updated child seat guidance, which will echo the pediatricians’ advice.

Child car seat use has dramatically reduced deaths and injuries in the last decade, but vehicle crashes remain the leading cause of death for children 4 and older. About 1,500 children younger than 16 die in vehicle crashes each year in the U.S., the Pediatrics report said.

Dr. Dennis Durbin, a pediatric emergency room physician at the Children’s Hospital of Philadelphia and the Pediatrics report’s chief author, acknowledged that some parents and children may balk at aspects of the new policy. Durbin is a father who understands that older kids are expert negotiators.

“There are certain things I’m willing to negotiate — bedtime, teeth brushing, broccoli for dinner — but safety is non-negotiable,” he said. “If parents establish that early in life, they’ll get less push-back over time.”

Durbin recommends that parents who have turned a child to face forward on her first birthday now reinstall that seat to face the rear of the car. Many parents believe larger toddlers will be uncomfortable in rear-facing seats or will hurt their legs in a crash, but Durbin said they are mistaken.

When researchers at Durbin’s hospital looked at children between the ages of 1 and 4 who were hurt in wrecks, leg injuries were rare for those in rear-facing seats, even though they are the second most common injury for those in forward-facing seats, he said. That’s because the legs of a child in a forward-facing seat are thrown forward in most crashes and can hit the console or the back of the driver’s or passenger’s front seat.

In a rear-facing mode the seats act like cocoons in an accident, cradling children’s heads, torsos, arms and legs and spreading the crash forces over a larger area.

Responding to concerns about comfort, Durbin tells parents that it’s easier for kids to sleep in rear-facing seats because they are reclined, whereas, forward-facing seats often force nappers to slump uncomfortably.

It’s the norm in other countries for children to remain rear-facing as they grow older. Kids in Sweden typically remain in rear-facing car seats until they’re 4, Durbin said.

American parents should carefully read their child-restraint instructions to make sure their children remain within the height and weight limits. A toddler with a very long torso may outgrow a rear-facing seat before age 2, and a heavy preschooler may exceed the weight limit for some forward-facing seats with five-point harnesses.

But the good news for parents with big kids is that most child-restraint manufacturers now offer convertible seats that allow a child to remain rear-facing until they reach 40 pounds.