Shelby Martin sensed something was different with her third pregnancy. She was feeling pains she'd never experienced before.

Little did she know that she was carrying a record-breaking baby .

“I didn’t think I was going to survive!” Martin, a mom of four, tells TODAY.com. "My physical therapist later explained that he was essentially popping my hip joint out of socket."

On July 29, it all clicked for the 30-year-old from Dixon, Tennessee, when she gave birth to Cassian, a 12-pound, 14 ounce boy, one of the largest newborns ever delivered at Tristar Centennial Women’s Hospital.

Shelby Martin's pregnancy felt different ... when her nearly 13-pound baby was born, she understood why. (Courtesy Shelby Martin)

According to the American Pregnancy Association , most full-term babies (

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