Rachel Bilson 's baby bump was on display as she went shopping for baby essentials in LA  on Monday. The mother-to-be is often spotted with her boyfriend, Hayden Christensen , but she flew solo for this outing. Since news of her pregnancy  came out in May, Rachel has kept busy. She and Hayden recently returned from a nearly monthlong trip to the Caribbean , where she showed off her growing bump in her bikini. Though Rachel has changed a lot since her days on The O.C., one thing always stays the same — the 32-year-old actress is ageless. Try to guess her age  in photos from the past decade and see if you can tell the difference.