"I realized that so much of the pressure I was feeling was from outside sources, and I knew I wasn't ready to take that step into motherhood," she said. "Being a biological mother just isn't part of my experience this time around."
At 38, Cameron Diaz has not ruled out having children but she supports women who do and has considered remaining childless herself.
"I think women are afraid to say that they don't want children because they're going to get shunned," the actress told British Cosmopolitan in June 2009.
"But I think that's changing too now. I have more girlfriends who don't have kids than those that do," she said. "And honestly? We don't need any more kids. We have plenty of people on this planet."
As for whether she wants children of her own, Diaz said: "I never say never. I don't know what's going to happen. I could end up adopting half a dozen kids, or I could end up being the next 'octomum'."
For now, Diaz is the doting aunt, who's happy spending time with boyfriend Alex Rodriguez's two girls. "I have three nieces and a nephew. I know what it's like. I've changed the diapers. I've seen three births, so I totally get the whole picture," she told Parade Magazine in May 2009. "I don't think it's a compromise to have children. I don't think it's a compromise not to. I think it's just a different choice."
She's still wrestling with her choice, however. Last June, she told In Style: "Having children changes your life drastically, and I really love my life. Children aren't the only things that bring you gratification and happiness, and it's easier to give life than to give love, so I don't know. That kind of change would have to be either very well thought out, or a total mistake -- a real oops!"
Helen Mirren has been with her husband, director Taylor Hackford, for 35 years, but long before then she decided against having children.
In a 2007 interview on Australian television, Mirren, now 65, revealed that she was deeply disturbed by an educational childbirth film when she was a teenage schoolgirl.
"I swear it traumatized me to this day," she said on the show, Enough Rope. "I haven't had children, and now I can't look at anything to do with childbirth. It absolutely disgusts me."
Asked if the film was the reason she never became a mother, Mirren replied: "I think it's a lot to do with it. I think in deep, proper psychological terms I was traumatized."