Then you'll most definitely wish to BE SURE that the man who is to be the paternal parent is ON the birth certificate, otherwise, baby welfare would most definitely wish to prove the baby is YOURS, biologically, if that baby is not properly provided for. The baby would be the innocent party to a rather silly game of sexual sensationalism, of which you, along with the couple, could find yourself a participate. Its sort of like you going with a couple guys to rob a grocery story ... you being the driver of the car ... yet, somehow the robbery gets botched and the store owner gets killed by one of the other guys. Guess what, YOU, as an accomplice to the robbery, would be just as guilty of the killing as the one that actually did the killing. Just the way the law works.
There's that old saying "in for a penny ... in for a pound"!