The couple, who were wed in a secret ceremony in Idaho on June 24, decided to go public with the pregnancy because Washington is set to host Saturday Night Live this weekend, and she "didn't want the focus to be whether or not she has a bump," a source said.
"Kerry and Nnamdi are ecstatic," the source said.
Washington has been so tight-lipped about her relationship with Asomugha that their wedding, five months ago, came as a complete surprise.
"I've had earlier times in my career when I did talk about it," she explained. "But I couldn't just turn around and say, 'I only want to talk about the good stuff, but not the bad stuff.' So I just thought, 'Okay, no more.'"
But with a ring and a baby bump to go along with it, Washington said she tries to be polite.
"I'm walking around in the world with my ring. And when people say congratulations, I say thank you," she said. "But I'm going to continue to not talk about it and just let it unfold."
As for Asomugha, he will be well rested because the 49ers have a bye this week.