Rizer revealed on her blog that she gave birth to son Alexander Rafahi 'Zander' Mehran III on Wednesday (November 23) "near San Francisco".
"Alex and I are very proud parents and incredibly excited to get to know our new little lad," Rizer beamed.
Describing her newborn, Rizer wrote: "He has 10 fingers, 10 toes, sandy hair, deep blue eyes and is practically perfect, in every possible way!"
Mehran and Rizer tied the knot in September 2010 in Lake Placid, NY.
The model has appeared in several films and television shows, including Sex and the City and Prince William and Catherine: A Fairytale Wedding.
She is also an HIV/AIDS research advocate, having been inspired to help those suffering from the disease when her own father Kevin Rizer died of AIDS in 1992.
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