TULSA, Oklahoma - A couple who struggled with infertility for years is now a family of six thanks to embryo adoption.

Embryo adoption has been around since the ‘90s but the number of births doubled in the last five years or so. A Green Country couple had their daughter through the process, followed by twin boys who were frozen for eight years before birth.

"It's such a roller coaster of emotions,” Melissa Smart said. “Definitely toughens you up.”

Melissa Smart and her husband Tom struggled to start a family for years until they discovered embryo adoption.

Tom: "First I thought, ‘What is this? This doesn't make any sense. How is this even possible? Is it even ethical?’"
Melissa: “That sounds like a sci-fi movie or something, I was like, 'Absolutely not.’”
Tom: "There's always that echo in the back of your head, 'Are we playing God?'”

Tom, a preacher, said after a lot of research and soul-searching, they decided it was out of their hands.

"If God wanted us to have children through this process, he would allow it," he said.

The couple went to the National Embryo Donation Center, in Knoxville, Tennessee, to go through the process of embryo adoption.

Two embryos were transferred to Melissa’s uterus, but she didn't get pregnant. Then, doctors transferred three more, including Addy, their daughter, who had been frozen in time for five years.

The couple decided to try to expand their family two years later and tried again with embryos that were Addy's biological siblings. They got pregnant right away but lost the baby.

"Even now, talking about it I get really emotional, especially since it's my daughter's biological sibling. I had hopes and dreams of that child,” Melissa said.

So, they adopted three more embryos, and when that didn't work, they went a different route.

"We're like, 'Let's just foster.' We get our foster son, and then the third time we get pregnant with our twins.”

The twins, Jonathan and Jerimiah, spent eight years at -196 degrees Celsius, frozen in liquid nitrogen.

"Twins are pretty common. About a quarter of our births are twins,” said Dr. Jeremy Keenan.

Keenan said the center's success rate is 45 percent, and most embryos are frozen in liquid nitrogen for six to 10 years.

“It's somewhat uncommon for a couple to go through IVF, create embryos, and then release their extra, or remaining embryos, just a year or two later. It usually takes them some time to, first of all, realize they don't want to have more children, and then, often times, it is quite a dilemma for them in what do I do with these embryos," he said.

Families can store them, discard them or donate them, hoping they find a loving family.

"We've always wanted a big family, we just didn't know they would be so close in age,” Melissa said.

The Smarts admit it can be a handful.

"I mean, we had one child for three years. It was a huge adjustment for her as well, all of the sudden having a brother and then three brothers, but now it's just our new normal," Melissa said.

It’s a normal they thank God for every day.

"You're taking all of these embryos out of the freezer and giving them a chance at life," Melissa said. "It's an amazing journey and I would do it all over again.”

Embryo adoption costs about $6,000 for the first try and $3,500 for the next. The center said it gives women three tries because if they aren't successful then it's likely her uterus isn't taking to the transferred embryos.

Couples do have to meet requirements like other forms of adoption. They also do a home study to make sure the couple is fit to be parents.