BOSTON - There's more scientific proof that there is such a thing as "pregnancy brain."

Every year, millions of pregnant women experience profound physical and hormonal changes, but what specifically happens to their brains? A team at University of California Santa Barbara performed 26 MRI scans on the brain of one neuroscientist before she got pregnant until two years after delivery. They found a significant reduction in gray matter volume, largely responsible for thinking, memory, and emotion.

That may sound bad, but experts say think of it more like pruning or prepping and fine-tuning the brain for more specialized tasks, which happens to children during puberty as well. Larger studies will look at the brains of hundreds of women pre- and post-pregnancy which may provide answers as to why some women develop pregnancy-related conditions like postpartum depression.