I believe there was a critically acclaimed play (and at least a few novels) written about this, at least they were written specifically back when the "gay gene" was in the news and people were speculating about whether early detection would lead to screening and abortions. While you can't rule something like this out, in reality, many people have considerable difficulty making a decision to abort, and few would tend to do so for non-life-threatening reasons.
You can take the fairly absolutist position the Catholic church tends to take, and forbid most if not all reproductive assists and procedures. That would have the benefit of making it harder to enable such choices in the first place. I'm not sure it would help things though.
When I look at things like this, I remind myself that, for example, if there is some day a way to objectively determine that a fetus is transgendered but not likely to show obvious outward signs of it in their genitalia, that the net result is likely to be a dawning realization of how unwise and unjust it is to coercively assign a gender at birth. That needs to change one of these days, and the more we come to know about natural diversity, the greater the hope that people will just learn to embrace those differences and leave everyone with a lot less anxiety and a better range of choices in life.
Perhaps it might lead to a society where transgendered people feel less need to risk major changes, or if that feeling does persist, the stigma attached will become no greater than the stigma attached to other forms of plastic surgery, or HRT done to cope with menopause, etc? Who knows? It's speculation, after all, at least for now.
Hopefully, it would lead to some more public debate, and maybe that in turn would lead to mothers like yours changing their thinking when it comes to cruelly and heartlessly saying things about wishing their children hadn't been born. Her sense of shame and what allows her to say that must be doing almost as much damage to her as it has done to you.
