Doctors informed Maddie Coleman at just 14 years old that she wouldn't be able to carry a baby.
Coleman was born with Mayer-Rokitansky-Küster-Hauser, a condition that causes the uterus to be underdeveloped. It was then that Coleman's mother, Megan Barker, said if she wanted to have a child one day, she would carry it for her.
"She told me at 14, but I wasn't thinking about having kids," Coleman told InsideEdition.com.
Coleman said she thought the offer was weird then, but when doctors told Coleman in 2013, at 23 years old, that she had a tumor on her right ovary that needed to be removed, she had to take things seriously.
Doctors told her that she should consider her fertility options because she may not be able to have biological children after the surgery.
Ten years after her mom's promise, it was time for Coleman to take her now 48-year-old mom at her word.
"I was possibly about to lose the opportunity to have a child," said Coleman. "After I found out I couldn't have kids, the idea of having a biological child was really important to me."
Coleman talked to her then fiancé, Tyler Coleman, about the decision.
The family decided to go through IVF and Coleman had 12 of her eggs frozen.
In February of 2016, doctors implanted two eggs into Barker, along with Tyler's sperm, and just the next month, on the day before Coleman's wedding, she found out her mom was going to be having their baby.
"I cried. I was very grateful. I was super emotional," said Barker. "For me to be able to have a biological child filled that void that I felt like I was missing. My mom is my best friend. I can't imagine anyone else doing this for us."
Gus was born to his grandma on October 22 in a room full of 13 people.
"She had a really easy pregnancy. The whole family was involved. We talked every day," said Coleman.
And now Barker is just like any other grandma, Coleman says.
"She spoils him. She loves to come over and help with baths and changing," said Coleman.
Barker said carrying her grandson was incredibly worthwhile.
"I think every mother wants what is best for their child in our situation. I know that Maddy wanted to be a mom. If that was important to her than it was important to me," Barker told InsideEdition.com. "I love my grandson. It is the best feeling ever and to be able to see Maddy and Tyler be the parents."