Heidi Klum looks quite literally fit to pop during a family day out at Santa Monica Pier over the weekend.

Dressed in a black clingy dress, the German-born beauty showed off an almost gravity-defying bump as she snapped pictures of her children as they played on the attractions.

Despite this being Heidi's fourth pregnancy, the model says she is always amazed at how her body transforms when she's expecting.

“It’s hard when you don’t fit in your things anymore," she said at three months.

"The last month is unbelievable, how rapidly your stomach goes. It’s huge. The thighs, the butt - everything explodes in the end. But it’s bizarre.

"Just as it’s a miracle that you can grow a human being in your belly, it’s a miracle that your body goes back to normal again.

"I don’t think you ever get back to exactly the way you were, but you do get close. And I’m happy with that. Especially when you see your kid for the first time.”

Baby number four - Heidi's third child with husband Seal - is due...about now!