Credit: Peter Kramer/NBC/NBC NewsWire

Giuliana and Bill Rancic always knew they'd be parents -- they just didn't know how.

After several failed IVF attempts and a miscarriage, the couple will welcome their first child later this summer via gestational surrogate. "The baby is 100 percent genetically ours," Bill, 40, tells Us Weekly. "It's our embryo."

When Giuliana was diagnosed with breast cancer in 2011, "we had the embryos frozen," Bill explains. "Everything happens for a reason, and we believe this is meant to be and the way it was supposed to work out."

He adds: "If she'd gotten pregnant, it probably wouldn't have been a very good outcome because of all the hormones -- it would have made the cancer surge. So this was the best option."

Though she's now cancer-free, doctors warned E! News host Giuliana, 37, that they would likely have to wait "three to five years" before trying to conceive a child on their own. "As soon as we heard that we moved forward with this plan," she tells Us.

"We go to this great clinic called CCRM and it was through our doctor, Dr. Schoolcraft, who referred us to the agency," Giuliana explains. "That's how we found [our surrogate]."

Though they've chosen to keep their surrogate's identity private, Bill says she's "a really nice girl who comes from a good family. Knock on wood, but  I think we hit the gestational carrier lottery!"

The couple had "thought about" adoption, too, "but we hadn't started the process," Giuliana says. "One baby at a time!"

After years of struggle, the spouses of nearly five years are excited to share their happy news with the world. "The last year and a half we'd been having people come up to us and shed tears and cry," Bill tells Us. "It's so nice now to be crying tears of joy. It couldn't be better."