MINEOLA, N.Y. (CBSNewYork) — New York has become only the 10th U.S state to pass the child safety seat law, but many parents may be unaware of the new requirements.

It went into effect Friday, CBS2’s Jennifer McLogan reports.

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The law used to require children sit in rear-facing car seats until they’re 12 months old. It’s now 2 years old, or longer depending on weight and height.

The new law seeks to better protect vulnerable babies and toddlers who often have disproportionately large and heavy heads and are at risk for serious head, neck and spinal injuries when thrown forward in forward-facing car seats.

“With the infant 2 years and under, they have a slightly larger head compared to their body, which, although it makes them quite adorable, also puts them at increased risk for instability,” said Dr. D’Andrea Joseph, of NYU Winthrop Hospital.

Lauren Paterno is mom to 2-year-old Hudson, who now by law must be buckled into a rear-facing car seat. Hudson weighs less than 40 pounds and is shorter than 49 inches, which are requirements for his seat, so he may stay rear-facing for another year, at least.

“It just gives me a sense of relief. Just as a parent, I want to make sure my child is safe and I know rear-facing is best,” Paterno said.

The number of crashes that children were involved in last year is staggering.

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“The latest statistics show more than 4,000 children were killed or injured in crashes in New York State,” said Robert Sinclair, of AAA Northeast.

Of those injured, 25% were not in rear-facing seats and 33% of the children who died were in no restraints at all.

“It’s really scary. As a parent, you never want to hear those kind of numbers and never want to think about that for your own child,” Paterno said.

“We’ve got a lot of work to do to get parents to put their kids in seats first, and then make sure they are in the proper seat and then make sure that seat is rear-facing,” Sinclair said.

Some parents worry about fussy babies and toddlers who want to see mom and dad while riding in the car, but doctors say that is far less important than keeping children safe.

And don’t worry about their legs.

“Children are very flexible. They can put their legs on either side of the seat. We are more concerned with head and spine injuries,” said Shani Jarvis, certified child safety seat technician.

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Car seats differ by manufacturer. Most are built to accommodate children up to 49 inches tall and a weight of 40 pounds.