Frank Micelotta/Getty Images Heidi Klum at the 2003 Victoria's Secret Fashion Show
In an Instagram post celebrating Leni's milestone on Tuesday, the supermodel and television personality, 47, revealed that she had actually walked the Victoria's Secret runway while pregnant with her eldest daughter.
Sharing a video from the 2003 Victoria's Secret Fashion Show, which featured Heidi wearing the lingerie label's "Very Sexy" Fantasy Bra, the mother of four wrote in the caption, "I am not alone walking down that catwalk here."
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Bill Davila/FilmMagic Heidi Klum at the 2003 Victoria's Secret Fashion Show
"If I look close enough then I can see you bumping right along at 4 months @LeniKlum," she added.
The America's Got Talent judge ended her post with a sweet note to the teen, writing, "I loved you before you were born, and I will love you long after I close my eyes forever. ❤️❤️❤️."
Heidi gave birth to Leni in May 2004, right after her split from Italian businessman Flavio Briatore. In December 2009, Leni was adopted by Klum's now-ex-husband Seal. Klum married Tokio Hotel musician Tom Kaulitz in July 2019.
Heidi Klum/Instagram Heidi Klum (left) and daughter Leni Klum
She recently graced the front of Glamour Germany, calling the milestone moment — which marked her first solo fashion cover — a "dream come true" on her Instagram.
Heidi opened up to PEOPLE about her daughter's blossoming modeling career in February, raving that Leni has "been doing fantastic. She's been wanting to model for quite some time."
RELATED VIDEO: Heidi Klum's Daughter Just Hit a New Milestone!
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"She opened Berlin Fashion Week where I saw her walk for the first time, in heels like as a real fashion model. It's mindblowing to me to watch her work, especially the first thing I did together with her and now she's doing things by herself, even though I go to the set," Heidi said.
"Obviously, as a mother, [I want my] child to do what she wants to do. The industry is great and I love it and I've been in it for over 20 years but it's also, it's a lot of traveling, it's different," she explained, adding, "You have to be a strong person, especially as a woman you have to be very strong."
Watch: Heidi Klum's teen daughter Leni is following in her mother's footsteps