'Miracle' triplets come home from NICU, joining 4-month-old big sister

This year, a couple who tried for eight years to become parents will celebrate Christmas at home with their four children, all of whom are under four months of age.

Zac and Britney Wolfe, of St. Mary's, Pennsylvania, on Monday brought home their triplets, Noa, Knox and Navie, who spent nearly 50 days in the neo-natal intensive care unit (NICU) after their Oct. 19th birth.

At home, the triplets joined their older sister, Charlie, who was born in July, just three months before their birth.

"Charlie finally got to meet her sisters and brother after 46 days in the NICU," Zac Wolfe told "Good Morning America." "Four babies under four months old may be quite the challenge, but we've got this. We have a great support system and have a lot of help."

A house full of babies is a welcome sight for the Wolfes, who struggled for many years with infertility, undergoing multiple rounds of both intrauterine insemination, or IUI, and in-vitro fertilization, or IVF, with no success.

The Wolfes said they were told by doctors they had "unexplained infertility," meaning tests showed no obvious cause for their fertility problems.

As their infertility struggles continued, the Wolfes began to pursue adoption, both the adoption of a child as well as embryo adoption.

With embryo adoption, a person can choose an embryo that has been donated, and then carry that pregnancy themselves. The embryo donors are people who have unused, frozen embryos left over from the IVF process.

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After several instances of false hope with adoption, and one failed attempt at embryo adoption, the Wolfes had two strokes of success, within a matter of months of each other.

Earlier this year, the Wolfes got an unexpected call from a neighbor asking if they were still interested in adopting a child. The couple said yes, and then were introduced in March to a local pregnant woman who wanted to pursue adoption.

"We met with her and she asked us if we would adopt her baby," Brittney Wolfe told "GMA" in an interview in October. "So, we were there from about the middle of her pregnancy. I was with her at her 20-week ultrasound when we found out it was a girl. I was there through all of her appointments."

At the same time, the Wolfes decided to continue pursuing another round of embryo adoption as well, in case either one of their options failed.

"We knew both of them may not work. It's a 50-50 chance," said Brittney Wolfe. "So we went for it."

In April, the Wolfes traveled to Tennessee for another embryo transfer, and found out that the transfer resulted in a pregnancy. The couple had transferred three embryos and, due to the quality of the different embryos, said they were told there was a less than 1% chance the three embryos would result in triplets.

Despite the odds, the Wolfes learned through an ultrasound exam that they were, in fact, expecting triplets.

The timing of Brittney Wolfe's pregnancy meant she was 20 weeks apart from the pregnancy of their adopted daughter's birth mom.

The Wolfes adopted their oldest daughter, Charlie, shortly after her July 27 birth.

Despite carrying multiples and having suffered previous miscarriages, Brittney's Wolfe pregnancy with the triplets went smoothly. She delivered the babies -- Knox, Noa and Navie -- via C-section on Oct. 19, 30 weeks into her pregnancy.

"When you're going through this, you're so stressed out," Zac Wolfe said. "And when Charlie came to us, I think that we weren't stressed as much, and Brittney's pregnancy went so good because we weren't focused on the negative. We got Charlie. We were so happy, and Brittney's pregnancy went amazing."

Now as they look ahead to spending the holidays together as a family of six, Zac Wolfe described 2023 as the "best and craziest" year of his and his wife's lives.

"We are so blessed," he said.