Rachel Bilson was still pregnant at the end of the series although her character Zoe had already given birth.
Autumn Reeser, Jaime King and Rachel Bilson all played in The O.C (2003)
Last episode of the series
In the final scenes, Zoe is hidden behind large objects such as bunches of flowers and Scarlett Kincaid. This is because Rachel Bilson is still pregnant even though Zoe has given birth.