After having a baby at 54, Brigitte Nielsen says she's 'never been happier in my life'

"The best part of being a mom at my age is being my age," Nielsen said.

Brigitte Nielsen, who made worldwide headlines earlier this year when she gave birth at age 54, opened up about motherhood and her baby, saying that now at age 55, she has "never been happier in my life."

"The best part of being a mom at my age is being my age," Nielsen told ABC News' Kayna Whitworth. "I'm mature. I'm very, very happy. I've never been happier in my life."

Nielsen and her husband Mattia Desi, 39, welcomed their daughter, Frida, in June, after the couple spent 10 years trying to get pregnant. Nielsen has four sons, who are currently in their 20s and 30s, from previous relationships.

"Ten years, we all know, it's a decade. Oh, decade sounds even longer, wow," Nielsen quipped. "It's a long time. But she is here, we didn't give up."

The long journey "has made us come even closer," Nielsen added of her relationship with her husband, adding that through "the most terrifying, sad moments" they were able to, "feel like we have each other."

As much as they wanted to start a family together, Nielsen said doctors were only giving her a 2 percent chance of getting pregnant using in-vitro fertilization treatments.

"The most difficult thing [the] first time was you think you're going to be pregnant, because everything is so ... technology, it sounds perfect," she said. "And you don't realize yet, how difficult it is, the whole journey."

"I think that first time for both my husband and I, they said it's negative, I broke down," she added. "I was devastated."

After ten years of trying, when the couple finally got a positive pregnancy test, Nielsen said doctors still urged her not to share the news with others yet because of how high-risk her pregnancy was.

"At my age ... at three months, you're not safe," Nielsen said. "At four months you're not safe. At five months you're not safe."

She added that her doctor said, "'If I were you, I would wait till you're 27 weeks, because at 27 weeks, no matter what happens, you're going to be okay.'"

Finally, at 37 weeks, the couple welcomed little Frida into the world via Ceasarian section.

"It was incredible," Nielsen said. "When you have a high risk pregnancy ... it's always in the back of your head, 'Is today going to be okay?' Of course, you cannot run away from it."

Nielsen said that her message to other women around her age who are considering IVF is to ask yourself if you can "psychologically deal with it."

"You have to look into your soul," she said, "and you have to read a lot."

"Ask yourself first, if you think, can you do that?" she said. "It depends how much you desire it, and how much you want it, and can you handle it? Can your body handle it? Can you psychologically deal with it?"

Nielsen also blasted the double standard that many older mothers deal with that she says older fathers are often immune to, saying that people "can get really mean."

"I was really worried about what people ... would say, 'How dare she? She's 54. What about the baby? What if she's going to die?'" she said.

"Trust me, you go through so many tests that they won't even allow you to attempt to have a baby if you're not in super health, so that's first step," she said.

Nielsen added that her husband is "15 years younger than me."

"So in this case, Frida will have an older, gorgeous, wonderful, mature mom, and she will have a fun exciting, younger dad," she said. "So she's got the best of both worlds."

Nielsen said she is now working to take care of herself so she can be there for Frida, and is looking forward to what the future has in store for them.

"I really have to take care of myself. Eat right, work out right, be happy, teach her good things, but be realistic about it, too," she said.

"We've made a choice. Yes, I have to be realistic that in 15 years, she'll be 15 years old, I will be 70," she added. "I will look 50, honey, I better."