Leighton Meester and Adam Brody have been parents a lot longer than people knew ... and TMZ has uncovered the name and gender of their down-low baby.
According to the birth certificate obtained by TMZ, Meester gave birth to a girl on August 4 ... not last week, as has been reported.
The girl's name is Arlo Day and she was born just after midnight at a hospital located about 30 miles away from Cedars-Sinai Medical Center, the usual celebrity hospital of choice.
The couple was married in February 2014 in a very hush-hush ceremony.
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