Article here: http://archive.is/aCxYc

This study, published in Nature Neuroscience, looked at the brain scans of women ... after they gave birth, and two years later, to see how the brain changed.  The researchers found "substantial" reductions in the volume of grey matter in the brains of first-time mothers.  The grey matter changes occurred in areas of the brain involved in social interactions used for attributing thoughts and feelings to other people - known as "theory-of-mind" tasks. 

So it's now proven that women literally lose a chunk of their (already limited) "theory of mind" brainpower during pregnancy.

Let's see what conclusions the researchers come to, with zero evidence:

The researchers thought this would give new mothers an advantage in various ways - help them recognise the needs of their child, be more aware of potential social threats and become more attached to their baby. 

Why would they conclude this: Well, let's take a look at the Wikipedia "Women are Wonderful" article:

The phrase was coined by Eagly & Mladinic (1994) after finding that both male and female participants tend to assign positive traits to women, with woman participants showing a far more pronounced bias.  

TL;DR: Science proves women lose their brains during pregnancy, researchers conjur out of nowhere that this makes women even more wonderful than they were already.