Pregnant Heidi Klum is obsessed with black maternity clothes

Christian explained: "She's all about black. We made her some pieces from my Fierce Mama Maternity line and she wanted everything in black. I think she's trying to cover it a little this time. She's getting older and wants to be more sophisticated, not casual. She's trying to keep it a little quiet."

Heidi - who already raises three children with husband Seal - recently revealed her pregnancy style secrets, claiming her changing shape would not stop her from dressing sexily.

The model said: "I love to be creative and find cute things in between maternity and non-maternity. It's about finding good shapes. Cool tops. Right now for example, I love the skinny pants and blousier tops, and then when I get bigger, I like to bring the form back to the body. Then I like to show it off."

When she can't decide what to wear, Heidi always turns to a pair of black Balenciaga jeans which are low cut so sit underneath her tummy.

Heidi's trainer has spoken about her attitude to fitness while she is expecting, claiming she is intent of keeping in shape.

David Kirsch told People magazine: "Why should she do anything differently? Heidi had a beautiful body all throughout her pregnancies. She's very disciplined and dialed in to being healthy."