Bilson, 32, jokes about her age-defying appearance in the June issue of Health, on newsstands May 16.
"I've always looked young because I'm so short, and especially if I'm dressed down," she tells the magazine. "When I have a baby, everyone's going to be like, 'Awww, poor teen mom. Poor girl.' And Teen Mom is my favorite show. … I know, pathetic. But it's true."
Becoming a mother may not be too far away for the Hart of Dixie star, who says starting a family within the next few years something she'd like to do: "I can just see this little toddler waddling around the house."
Bilson has dated Hayden Christensen, 33, for seven years, and she says they have "grown up together in a way."
The actress also credits her time on The O.C. with keeping her grounded – and away from the party scene that claimed other up-and-coming celebrities.
"I grew up in L.A. and did all that when I was younger. I went to the clubs and did all the drugs and alcohol," she says. "I got it out of my system, so by the time I was on The O.C., I was like, 'Wow, I can just enjoy this.' Then I started dating a costar [Adam Brody], so it was more of a domesticated thing."
Bilson is still happy to be a homebody, watching TV shows like Family Feud with friends and keeping an early bedtime.
And though she's known for being fashion-forward, you won't find her favorite garments on the pages of Vogue.
"I'm really into the granny nightgown, I'm just gonna say. Like, full-on long-sleeve, long nightgowns. They're super comfortable!" she says. "They're cozy. You just feel free. You're like, 'Oh! I'm in a dress. But I'm sleeping!' I secretly wish I could be 80. If I could, I would be 80. It would be amazing."