Heidi Klum has sparked gossip she's expecting a fourth child after pictures of her designer maternity outfits were accidentally posted online, it's claimed.

“It looks like Heidi is four months pregnant,” an insider tells In Touch.

“Sketches leaked online of her in redesigned couture gowns to make room for a bump, but were quickly taken down!”

Heidi and partner Seal had reportedly hoped to keep their baby news secret for a little while longer.

“She plans to announce her pregnancy when she wears the dress [from the leaked photos] to the event,” adds the insider.

Heidi sporting a maybe-baby bump while out and about with Seal and the kids over the Easter break

The German-born beauty and Seal already have two children together, and Seal is the adoptive father to her daughter by Formula-1 mogul Flavio Briatore.

Revisit the 2008 Hollywood baby boom below