A while back, during the whole "gay sheep" controversy, I remarked that if homosexuality can be detected in utero, we're likely to start aborting gay fetuses long before we start trying to "cure" them, because "there will almost certainly be a period of years or decades when it becomes possible to estimate your child's probability of homosexuality in utero, but not to 'inoculate' said child against same-sex attraction." But the more I read about the state of the science on same-sex attraction, the less I'm sure that's right. Consider this fascinating article on "The Science of Gaydar", which has this to say about the state of the "what causes homosexuality" debate:
Because many of these newly identified “gay” traits and characteristics are known to be influenced in utero, researchers think they may be narrowing in on when gayness is set—and identifying its possible triggers. They believe that homosexuality may be the result of some interaction between a pregnant mother and her fetus. Several hypothetical mechanisms have been identified, most pointing to an alteration in the flow of male hormones in the formation of boys and female hormones in the gestation of girls. What causes this? Nobody has any direct evidence one way or another, but a list of suspects includes germs, genes, maternal stress, and even allergy—maybe the mother mounts some immunological response to the fetal hormones.
So even if homosexuality turns out to have a genetic basis, which I assume it does, it's perfectly possible to imagine researchers finding a way (as the article puts it) "to regulate hormone flow and direct the baby’s orientation" without attaining any of the breakthroughs in gene therapy that would be required to reengineer the genes themselves. (Whereas with Down's Syndrome, say, it seems - based on my admittedly sketchy understanding of the science - to be gene therapy, abortion, or nothing.) In which case you won't have genetic screenings for homosexuality that force socially-liberal parents to decide whether their commitment to gay equality outweighs their desire for grandchildren, and socially-conservative parents to decide whether their opposition to abortion outweighs their distaste for the idea of gay offspring; you'll just have a regimen of hormone treatments that promises to keep your embryo straight, which is something that both sides of the culture war will find much easier to justify.
Anyway, that's just one of the interesting issues the article raises, so go read the whole thing.