"The Biggest Loser" trainer Jillian Michaels spoke with Jay Leno last night about her two young kids -- and the somewhat unexpected way they came into her life.

Michaels explained that her daughter Lukensia, 2, and son Pheonix, 8 months, arrived in the course of four days. She and her partner Heidi Rhoades had been trying to adopt for some time with no success; finally, being “exasperated with the process,” Rhoades decided she would have a baby.

“To make a long story short, two years later I get a[n adoption] referral. ... Twenty-four hours later, [Heidi] came downstairs and said 'I'm pregnant.'"

Michaels was shocked by the news, she says: "I kept looking at the little line, I was like 'that's not very dark, there’s no way, I think you’re mistaken.'"

Of course, she wasn't -- and Michaels says she paid close attention during her partner's pregnancy. "It's a lie, it's not nine months; it's ten months. I counted every week for her."

When Leno asked if raising the kids was a lot of work, Michaels said, “It is truly amazing and there are moments when you look at your kids and you think, 'I can’t even believe the way I love this little person.' It’s the most foreign thing for me still. You’d jump in front of a train for them, obviously. But at the same time ... it’s hard work, man!”

That final comment echoes something Michales said in a People interview last year: "Parenting is not for sissies. You have to sacrifice and grow up."

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