Believe it or not, that very point has been made by a gay prolife group called PLAGAL (Pro Life Alliance of Gays and Lesbians.)
They say if "gay" turns out to be genetic, and abortion is legal, there'll be no way to prevent women from having the baby prenatally diagnosed and then killed if they didn't want a gay son or daughter.
They consider that legal abortion contains the potentiality of genocide of "pre-gay" unborn babies.
A paradox, hey?