Maybe momma herself didnt know who the real father was?
Boom!
There it is right there.
I read something last year that said it was common around the time Obama was born for someone at the hospital to sell the birth certificate to Japanese immigrants so their child could be citizens. So that's most likely why no birth certificate. That one released by the White House is fake as shit and he may end up impeached and jailed over that. Also; check google for nakeds of obamas mama.