As much as my husband supports the whole message board thing, I cannot even tell you how upset, saddened, and even devastated he would be to know that the entire world of strangers on the Dis found out before HE did.
He would feel the same about me keeping the news from him for even an hour after I found out.
Of course, that would be impossible since he knew, I mean KNEW, very very very shortly after conception. Apparently my entire BEING changed, head to toe, and he was actually the one that bought me the stick to pee on, just so I would stop dithering and wondering. Even as newlyweds he knew me, my personality, and my body so well that he absolutely knew. So a surprise like this would be impossible.
I'd pull back on this one, tell him NOW, and stop it with the surprise. And maybe you'll find out he knew already.