This impulse was a normal human impulse i believe. You, on some level, and rightfully so, got a little jealous that he gets to stay at home all day and have fun while you work and take care of your baby. I don't think you did anything wrong, and the friend can't prove that it was you, so if you don't want to tell him, or volunteer the info, you don't have to.

I do understand the impulses and the acting on them, but I still think that what you did was a completely understandable and normal thing for a lady to do! I could totally see my wife doing this, under these curcumstances.