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Baldwin, 54, married the yoga teacher, who is 26 years his junior, in a July 2012 wedding in New York.
The child is expected in the summer, the spokesman said, but gave no other details.
The award-winning actor most recently played egotistical television executive Jack Donaghy on the NBC comedy "30 Rock," which broadcast its last episode in January.
Baldwin was married to actress Kim Basinger from 1993-2002. The couple have one daughter, Ireland, who was born in 1995.