Why do women get stupid during pregnancy?

Before my eyes, 6 colleagues at work were pregnant (literally, in one office). Duri did not notice, irritability and caprice too. All remained professionals in their field until the decree. Even the number of errors did not increase (and I, as an analyst, clearly track this fact due to the compatibility of tasks).

I was "stupid" only once - when we were visiting relatives, and one not very smart person decided to tell an anecdote about a pregnant woman who ate shit, and did not calm down until he told it to everyone in the house in turn. I was very hurt and unpleasant. Moreover, during pregnancy I led a normal life - I worked, traveled (even hitchhiked!), Ate as usual.