Theo Paphitis from Dragon's Den claims that pregnant women's brains 'turn to mush': here. Unless this is just journalistic licence, this man is clearly turning hearsay into fact.
The facts appear to be that the brain does shrink during pregnancy, which can impair intellectual function and possibly even cause PND. But this doesn't necessarily happen if you add extra fatty acids to your diet. I know of women who achieved great things before and after having a baby, what about you?
I'll start: I won an industry competition when 6 months' pregnant and was selected as one of my industry's 'bright young things'.