Baggy clothes? Hehe.
Seriously though, it sounds like you're applying for pretty top end stuff, so I would imagine that the academics involved are looking for the top people. Whether pregnant or not. They might want to know how you'd manage PhD and looking after a new-born child, whether you'd have to start late because of maternity leave and so on, but it really shouldn't affect their decision.
Any if it does - are they really the kind of people you want to work with?