Deschanel, 34, first announced her pregnancy in March. It was written into the Fox drama when Brennan told Booth (David Boreanaz) she was expecting after they finally hooked up off-camera. Bones' upcoming season was scaled back because of Deschanel's pregnancy, but Fox recently ordered four more episodes that will possibly air next summer.
Deschanel and Hornsby married a year ago. Her younger sister, Zooey Deschanel, now has two reasons to celebrate this week: becoming an aunt and her own Fox show New Girl premiering to robust ratings on Tuesday.
Bones returns on Nov. 3 at 9/8c on Fox. Hornsby stars in and executive- produces the new comedy, How to Be a Gentleman, which premieres Sept. 29 at 8:30/7:30c on CBS.