The American Academy of Pediatrics is now recommending toddlers stay rear-facing in car seats until age 2, according to a report released today. (See below for full report).

The AAP reports: 

Recent data shows why toddlers between ages 12 and 23 months who ride rear-facing in a car safety seat are more than five times safer than those riding forward-facing in a seat.

This replaces a previous recommendation that toddlers be rear-facing until age one. Other safety experts recommend rear-facing for "as long as possible"—this is the first report that specifies age 2.

The only hitch to this recommendation: some car seats won't be able to safely hold a two-year-old rear-facing. Why? According to CDC growth charts, the average weight of a 24 month old baby is 28 pounds (boys) and 26.5 pounds (girls). (FYI: We corrected these figures after a reader below pointed out our initial post overstated these numbers—we apologize for that).
While most convertible car seats work to 35 pounds rear-facing, a few models still only go to 30 or 33. Example: Combi's new Cocorro convertible seat only goes to 33 pounds. And the Combi Zeus is only 22 pounds rear facing. Most Britax seats, however, are 35 pounds rear-facing.
And remember that the 27-28 pound weight of a 2 year old is the MEDIAN figure—or 50th percentile weight. The biggest babies (100th percentile) would be close to 34 pounds by the time they hit their 2nd birthdays.
Bottom line: be sure you get a car seat that works rear-facing to at least 35 pounds. 

Above, we posted a link to a summary of this report that is on the AAP web site. The actual article in the AAP news is on their subscription-only part of their web site (that is, not viewable by the public). Since we've received so many queries about this today, we are reprinting the entire report below:

advice: Rear-facing car seats safer for children until they are 2

by Lori
O’Keefe • Correspondent

Toddlers between the ages of 12 and 23 months who ride
rear-facing in a car safety seat are more than five times safer than toddlers
in that same age group who ride forward-facing in a car seat.

Overall, children under the age of 2 are 75% less likely to
die or experience a serious injury when they ride in a rear-facing car seat,
according to the first U.S. data to substantiate the benefits of toddlers riding
rear-facing until they are almost 2 years old (Henary B, et al. Inj Prev. 2007;13:398-402).

There is a common myth that rear-facing toddlers whose feet
reach the back of the vehicle seat are more likely to suffer injuries to the
lower extremities in a car accident, according to a commentary co-written by
Marilyn J. Bull, M.D., FAAP, AAP District V chair and one of the co-authors of
the study. However, lower extremity injuries are rare with rear-facing seats,
Dr. Bull wrote in the commentary (Bull MJ, Durbin DR. Pediatrics. 2008;121:619-620).

Rear-facing seats are more likely to support the back, neck,
head and pelvis because the force of a crash is distributed evenly over the
entire body. Forward-facing children are more likely to be injured because the
force of the crash is concentrated on seat belt contact points, and younger
children’s heads are disproportionately large for their small, weak necks,
according to the study.

“I teach my medical students that parents worry about leg
injuries but that it is far better to send children to orthopedic specialists
to have lower extremities treated than to send them to neurological specialists
to have cervical spine injuries treated,” said Dr. Bull. “I put it into the
context of rehabilitation potential: fracture vs. paralysis.”

In Sweden, children ride in rear-facing seats until the age
of 4, which has been proven to be 90% effective compared to children who ride
unrestrained. However, car seats are engineered differently in Sweden to allow
older toddlers to remain rear-facing longer.

“Since motor vehicle injuries are the leading cause of death
in children, the Academy must do whatever it can to educate our members and the
general public about the safest ways for children to ride in motor vehicles,”
said AAP President David T. Tayloe Jr., M.D., FAAP. “We should make sure all of
our members know to encourage parents to keep their children in rear-facing car
seats as long as they do not exceed the size limits of the car seats.”

Dr. Bull noted that it takes less than 30 seconds to tell
parents that children are five times safer riding rear-facing until their
second birthday — a statistic that is likely to stick with parents.