The changes were all over the brain too — "over 80% of my brain regions showed reductions in grey matter volume," Chrastil said.

Grey matter is brain tissue with high concentrations of neuron cell bodies, where information is processed. Reductions in grey matter volume are sometimes associated with reduced memory and cognitive function.

However, the study authors say a reduction in grey matter during pregnancy isn't necessarily a bad thing. It's more like a wave of brain refinement as the brain prepares for motherhood — like the process of chiseling a block of marble into a sculpture.

Seems like an overly positive framing of the effect.