The Hunger Games star and her husband Max Handelman welcomed little Felix last March (11) after having problems conceiving on their own, but she largely kept the news under wraps.
Banks had trouble keeping the secret to herself around her 30 Rock co-star Baldwin because although she wasn't physically with child, she was preparing for her new arrival.
She tells Allure magazine, "Alec Baldwin asked me straight up - I had made a comment about wearing a fake belly (while filming What to Expect When You're Expecting), something innocuous and he looked me straight in the eye and asked me, 'Are you pregnant right now?' And I blanched totally. Because of course, technically, no I wasn't. But then, technically, yes, in a way I was!
"And it was very weird. I thought Alec was reading my mind or something. Well, we weren't telling anyone then, so I said no. I thought, is that a lie? Because it wasn't a lie, and yet it was a lie! It's essentially a test tube baby - its just the test tube is another woman. That you can grow a baby outside of yourself! Its amazing!"