Mary-Kate Olsen's tiny frame is reportedly hiding a mini Olsen. 

The famous twin is rumoured to be pregnant after her weight 'rocketed' up to a less frail - but still svelt - 120Ibs, according to US reports.

A source tells the National Enquirer, "Mary-Kate has been looking a lot rounder recently.

"It is good she has put on weight, because she previously suffered from anorexia, but a lot of people think she could actually be attempting to hide her pregnancy."

She hides it well: Is Mary-Kate playing hide-the-bump under some extra padding or has she just been tucking in?

Mary-Kate's sorely-missed friend Heath Ledger is said to have talked up the idea of having a baby and she reportedly feels now is the right time.

See stars before and after the bump below