The 32-year-old star took to Twitter to make the announcement.
Teigen, in a cryptic tweet, wrote, "Somebody's here!"
Legend, 39, also retweeted his wife's post.
The couple did not share any more details about the family's newest arrival.
They announced the pregnancy in November last year.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)