Actress Nia Vardalos has opened up about her struggle to become a mother in her new memoir, revealing she went through 13 rounds of fertility treatment before eventually turning to adoption.

The My Big Fat Greek Wedding star and her husband Ian Gomez have kept their battle to start a family private for years, but now, after taking in a three-year-old daughter, Ilaria, in 2008, she has gone public with her long journey to parenthood in new book Instant Mom.

During an appearance on U.S. breakfast show Today on Tuesday (02Apr13), she said, "I'm very persevering and tenacious to the point where I call myself a fearless idiot, but at that point, where you do one (in vitro fertilisation treatment) after another, it's because you're so in the pursuit of being a mother."

The couple eventually turned to adoption and they were soon matched with a young toddler from the U.S.

Vardalos explained, "She came to live with us with 14 hours' notice. And when Ian and I met her, we drove to a parking lot and the way it works with American foster care is you have a chemistry meeting. So the social workers were holding her in their arms and I knew nothing about her, and we walk towards her and all I saw was a little brown-haired almost-three-year-old little girl in someone's arms. And she turned and looked at me and my first thought was, 'Oh, I found her.'"

But the 50 year old admits there were some early difficulties as the tot adjusted to her new life: "From the minute she came to live with us, it was eyes downcast, she was withdrawn, she got very angry the next day, she bit my finger to the point where I was like, 'Medic!' It was really, really hard. She wouldn't let us hold her or kiss her... (but) within six months, by the time we finalised her adoption, she was completely transitioned and loving and attentive and attached."