Pregnant couple duped by Rolex thief

A brazen thief has stolen a $22,000 Rolex from a pregnant Melbourne woman and her partner, who met him after advertising the watch online.

The shaken couple, who wanted to sell the Rolex to help pay for their baby costs, posted it on Gumtree and then organised to meet the would-be buyer.

The trio met at a Westfield Doncaster shopping centre cafe, but the transaction went horribly wrong when the thief ran off with the watch after asking to try it on.

Detective Senior Constable Leanne Trusler said the thief might have planned the crime before he met with the couple.

"Selling a watch or piece of jewellery at that price, I'd be doing it through another means," Det Sen Cons Trusler said.

"It doesn't happen all the time, but it's an example of the dangers of selling online."

Police have searched for the watch at local pawn shops but are yet to find it.