I'm 41 and was told at my scan that unless my odds were worse than 1:150 they wouldn't even consider an amnio. My base odds before bloods and scan (so purely on age) was 1:59. I know it goes up dramatically with age when you get to be an old duck, I would have thought 1:300 was still a huge improvement on her base. Hugs to your sister. Its very stressful when people seem to do nothing more than look at your age and start with the bad news.