Hayes, 41 and a mother of three, is now fighting for her life against flesh-eating bacteria that have so far forced the amputation of her arms and legs.
"Everything was fine," said Katy's husband, Al Hayes, of the days following the Feb. 10 birth of baby Arielle. "She was sore but it was to be expected."
Never did Hayes expect that just a few weeks later, he'd be signing papers to allow doctors to remove his wife's extremities while she slipped in and out of a coma, unaware of what was going on around her.
"It was the worst day of my life," said Al Hayes, 34. "But Katy knows why I had to do it – I had to do it to save her life."
"Before this Katy was completely healthy – she had run a half-marathon and did yoga four days before she gave birth," said Hayes. "She'd work out five times a week."
Al took his wife to the hospital on Feb. 14, when the pain in her abdomen became more acute and persistent. Doctors determined that she had been infected with invasive group A streptococcal disease. In most cases, strep infections result in a skin infection or a sore throat, commonly known as "strep throat," and patients recover with a dose of antibiotics.
But Katy would soon learn that her strain of strep was a very different kind.
"Basically every vein and artery in her body was a giant hole, and she went into complete lung, kidney and liver failure," said Al Hayes. "Her skin started to blister and peel off on all of her extremities; everything from infectious fluids to blood would just weep through her skin."
"Her doctors told me that she had less than a five percent chance of surviving, and that 'nobody comes out of this' because once the snowball effect happens of organs shutting down, there is nothing medical science can do to reverse it," he said.
But the doctors' grim warnings only motivated Hayes to advocate for his wife's medical care even more, determined not to let Katy die without her doctors trying everything possible to save her.
Husband Fights for Wife, as Flesh-Eating Bacteria Ravages Her Body
"My responsibility is if she's going to die on an operating table I'm going to try to save her, we're not going to sit there and let her die, she's going to fight it, that's what she'd want," said Hayes.
Shortly after Katy was hospitalized, Hayes started a blog to chronicle his wife's condition, titled "Katy is Strong." It was a convenient way for him to connect with the rest of their family while still being able to focus on his wife's treatment.
In an emotional blog entry on Feb. 27, the same day he allowed doctors to perform the amputation of Katy's arms and legs, Hayes wrote, "I hope that everyone will understand why I did this. I hope that Katy will forgive me. I hope that I can forgive myself."
"It's a complete miracle that I'm alive, so I'm so grateful... I'm so grateful," Katy said. "I wouldn't be here for my kids if they wouldn't have taken my arms and legs."
According to Dr. William Schaffner, the chairman of Preventive Medicine at Vanderbilt University Medical Center, the strain of strep that Katy contracted used to be very common hundreds of years ago in women who had just given birth.
Now, Schaffner says, this type of infection is extraordinarily rare.
"The genetics of strep have changed," he said. "We don't see these outbreaks as frequently as we used to. But every once in a while one runs into a strain of a particular strep group A that has the capacity to cause serious invasive disease."
According to the Centers for Disease Control and Prevention, about 9,000 to 11,500 cases of the invasive strep infection occur each year, resulting in about somewhere between 1,000 to 1,800 deaths annually. In contrast, several million cases of the less serious strain known as strep throat are reported each year.
Schaffner says that the amputations Katy underwent are not uncommon for individuals suffering from the invasive infection.
"One of the ways to try to stop it is to try to get ahead of it and cut off the piece of the body where the infection is so it doesn't keep advancing," said Schaffner.
Schaffner also said that there is no way to know whether Katy's home birth made her more susceptible to the disease.
"It's like asking why did that person get hit by the truck, it's just that this is the strain of strep [Katy] happened to run into," he said.
Katy Hayes Looks Forward to Life with Kids
Enough of Katy's arms and legs exist that prosthetics will be an option in the future, said Hayes. But for now, Hayes is focusing on stabilizing his wife. Katy has moved to Parkland Hospital in Dallas, which has a burn-trauma unit that can treat her flesh wounds. She is also going through intensive physical therapy.
Hayes says that he hopes to take Katy home soon to their newborn, their 6-year-old son and her 16-year-old daughter. He knows it will still be a long road to recovery.
Asked why he decided to share his wife's story so publicly, Hayes said that he did to show others that patients sometimes need help advocating for themselves.
"I want people to know they have rights, and if you have a loved one in a hospital you can't afford to sit and just gieve and do nothing," he said. "You have to be active participants and educate yourself."
"My wife is an incredible woman," he said, "She's worked on the set of the 'Teenage Mutant Ninja Turtle' movies, has hiked the Alps and has been a massage therapist for 17 years."
"You took a woman with that much life and saw her wake up as a quadruple amputee," he said. "But it will be worth it. She's alive and we won't let her forever be just a torso."
"It's hard for me to accept praise what I've done for Katy," said Hayes. "I don't feel like there is any option, I'm just doing what anyone would do for someone they love."