The Boom Boom Pow singer also posted a mocked-up vintage snap of her and husband Josh Duhamel as children, clutching a startled feline.
If this cute pic is anything to go by, the LA-based pair's child will be a cross between Drew Barrymore in ET and a Von Trapp child with a penchant for picnic blanket gingham.
Congratulations to the happy couple and their brand new hump/lump/bump!
Six big family moments that matter – and the products that make them easier to navigate
These products from John Lewis & Partners help support the memorable moments of family life.