The Gossip Girl and O.C. alums, who were married in 2014, welcomed a baby girl on Aug. 4 and named her Arlo Day, according to TMZ. (Initial reports said Meester gave birth last week.) Much like their wedding, which also was kept under wraps until after the fact, the couple did not publicly announce ahead of time that they were expecting.
(Disclosure: TV Guide is owned by CBS Interactive, a division of ViacomCBS.)