Radio and TV host, music director and Playbill.com writer Seth Rudetsky first went public with the news Aug. 4, sharing a photo of a pregnant Block on Twitter.
Following the news, Arcelus also took to Twitter to express his thanks for the well wishes.
Block has performed in Little Miss Sunshine, The Mystery of Edwin Drood, Anything Goes, 9 to 5, The Pirate Queen, The Boy From Oz and Wicked. Arcelus, who also appears in "House of Cards," has been seen on Broadway in A Time to Kill, Elf, Jersey Boys, Good Vibrations, Wicked and Rent. Block and Arcelus, who met while appearing in Wicked, were married in 2007.