Chrissy Teigen and John Legend have quietly welcomed baby number four.

The cookbook author, 37, announced the news in a lengthy post on Instagram, sharing how she had always wanted four children, and it has now become a reality.

Their son, Wren Alexander Stephens, was born on June 19 via surrogate.

"We want to say thank you for this incredible gift you have given us, Alexandra," she said.

"And we are so happy to tell the world he is here, with a name forever connected to you, Wren Alexander Stephens."

"Our hearts, and our home, are officially full. And to our Jack, we know both their angel kisses are from you."

While Legend, 44, shared a photo on Instagram with all four of his children.

"Wren Alexander Stephens, our new love," he captioned the post.

The couple's new arrival comes just five months after the family welcomed baby number three, a girl.

"She's here! Esti Maxine Stephens - the house is bustling and our family could not be happier," Teigen wrote on Instagram.

"Daddy sheds nightly tears of joy seeing Luna and Miles so full of love, and I am learning you still need diapers with a c-section!?"

Teigen first posted her pregnancy news on Instagram last year in August, alongside photos of her growing bump.