(Newser) – The first study of its kind shows that newborns' brains grow fast—figure a staggering 1% a day immediately after birth, though it slows to about half that rate by the end of three months. Using MRI scans of 87 newborns' brains, researchers discovered that the first weeks of life see the fastest growth—those little brains grow by 64% in three months. The cerebellum, responsible for movement, grows the fastest and the memory-forming hippocampus the slowest, LiveScience reports. Researchers from UC San Diego and the University of Hawaii took more than 200 MRI scans of full-term and preemie babies, starting when the kids were just 2 days old. The scans found that preemies' brains are 2% smaller than average at the end of 90 days, suggesting that medically unnecessary induced labor can stunt a baby’s brain development, says UC San Diego's Dominic Holland.

"The brains of premature babies actually grow faster than those of term-born babies, but that's because they're effectively younger—and younger means faster growth," he adds. Researchers say using MRI or CT scans will prove to be a much more effective way to track development. Scans should lead to more exact growth charts—replacing the old method of measuring the skull with measuring tape—and help identify disorders such as autism or brain injury early. Researchers plan to look further into how alcohol and drug use during pregnancy affects brain development. (Meanwhile, scientists dispel the notion that we use only 10% of our brains.)

