It’s not entirely clear why, but the number of babies born with cerebral palsy appears to be decreasing, a new study suggests.

Researchers in the Netherlands looked at nearly 3000 babies born prematurely — meaning they were at high risk for cerebral palsy — between 1990 and 2005.

Of those born in the early part of the study period — 1990 to 1993 — 6.5 percent had cerebral palsy. But a decade later, the rate of occurrence dropped significantly to 2.2 percent for babies born between 2002 and 2005, according to findings published Thursday in The Journal of Pediatrics.

What’s more, the children born during the later part of the study period who were diagnosed with cerebral palsy had more mild cases of the condition than those born earlier, the study found.

The improved outcomes could be due to improvements in care before, during and after birth over the 15 year period, researchers say.