This was an interesting reply. As some replies noted, not all problems addressed by (say) surgically-assisted births and (some) vaccines are heritable. So it would take a long time for a vulnerable subset to emerge. Once it emerged, the medicine we take for granted could easily erode over a century into something less dependable (there are places in the world now where safe OB services are nonexistent, nevermind vaccines). So it need not be a catastrophe, just a gradual diminution of quality and availability.
And no I am not suggesting we deny medical services to anyone. I am wondering about an eventuality that I hope is purely academic.