A Kentucky woman has given birth to her niece, after volunteering as a surrogate for her sister-in-law.

Already a mother of three, 32-year-old Rachel Wilcox offered to carry a baby for her sister-in-law Amanda Peterson, 33, after she was left infertile by stage three colon cancer.

Wilcox, who's married to Peterson's brother, Micah, discussed the possibility of acting as a surrogate with her husband, when her doctor suggested it at a check up.

"Her words stuck in my head. After I discussed it with Micah I suggested it to Amanda and [Wilcox's brother] Reid," Wilcox told Daily Mail.

"Luckily, they accepted and now have Adalyn Rae, the baby they longed for," Wilcox said. "Seeing the immediate mother and daughter bond between Amanda and the baby was incredible."

On September 22, 2017, Wilcox gave birth to Adalyn Rae Patterson - who was named after her - at The Christ Hospital in Cincinnati, Ohio, to the joy of her entire family.

"I have an incredible bond with Adalyn, but she doesn't feel like my child," Wilcox said. "She's a part of my story, but I have a connection with her that's different to my own children."

"When I saw her for the first time with Amanda, I could see that mother-daughter bond straight away, and that was so beautiful," she said.

But this wasn't the only selfless act Wilcox would offer.

Following her delivery, Wilcox told her sister-in-law she would act as their surrogate again, should they want to expand their brood.

"At the moment, Amanda and Reid are concentrating on being great parents to her, but, if they ever want a second child, I would happily be their surrogate again," she said. "For them to have a family of their own is more important than my own needs and comforts."

Peterson, who has described Wilcox as "the most selfless human being I know," was left crestfallen after her chemotherapy and radiotherapy treatment left her infertile, leaving her with little hope to being able to have a family some day. Luckily, she was able to end her treatments on September 2015.

However, with Wilcox's persuasion, they decided to take her up on the offer, and had their embryo implanted in Wilcox's womb.

"When Adalyn was born it was the most magical feeling, she was totally perfect," Peterson said. "We had waited to for that moment for so long and thought it would never come. I was the first one to hold her and it was incredible having the skin-to-skin time, it just felt so right."

"Throughout Adalyn's life we will explain to her the amazing thing her aunt Rachel did for her and for us," Peterson said. "She's sacrificed so much and we will never be able to repay her."

Do you know anyone who's started a family with the help of surrogacy?