I think kegamine is pointing to the grammatical oddity of using the singular "woman" in the title, rather than the plural "women":

  Pregnancy alters woman's brain

The article introduction phrases this in a little more concise a way:

  Pregnancy reduces grey matter in specific parts of a woman's brain

I can see how the introduction probably became contracted to form the title, but in the contracted version, the plural "Pregnancy alters women's brain" would seem a little more grammatically precise than "Pregnancy alters woman's brain".