'Six-pack mom' Sarah Stage shares first photo with 7 pounds 2oz newborn baby

Hours after welcoming her second child, fitness model Sarah Stage − who rose to her fame thanks to a barely-there baby bump − has shared the first picture of her newborn son.

In the heartwarming picture taken in the hospital, she poses with her baby Logan Alexander as her husband Kris Jason and their two-year-old James Hunter watch on smiling. Her second child arrived via C-section on Monday (October 16).

"Welcome to the world, Logan Alexander. Born October 16th at 1:20pm #7pounds2ounces," she captioned the post.

"We prayed, planned, and wished for a healthy and happy baby boy. We received all we wished for and now our family is complete. Thank you for all of the support, we appreciate it!"

She was soon inundated with congratulatory messages, with one person writing: "Congrats just started following u n ur an unbelievable motivation [sic]"

Another of her 2.3 million followers said: " I'm so happy for u, I was waiting for this baby more than u lol."

Even into her third trimester, Stage maintained a svelte shape, leaving many people perplexed. She only gained 18 pounds. "HOW?! HOW DID THAT BABY COME OUT OF YOU?! You were so tiny! My mind is blown," one person wrote.

The 33-year-old online sensation was often body-shamed by trolls who slammed for sharing her workout videos and photos flaunting her toned physique.

She addressed the backlash in an Instagram post, telling her critics: "Since I've announced my second pregnancy, I've had certain 'Instagram medical experts' tell me what I should and shouldn't do."

The Californian added, "It feels great to prove ignorant people wrong & even better to know that all you have to do is believe in yourself and trust your own instincts With that being said, I hope you have a great day!"