Hi Zoe
I'm in the same position right now. Apparently a risk factor for chromosomal problems issues is considered high at 1:300. We were given risks of 1:3 Downs and 1:4 Edwards. We are currently awaiting amnio on 3rd May.
There's a link here on Edwards to get you started. It's when there are three chromosomes on number 18. Generally the syndrome is considered incompatable with life. Most fetus 95% don't make it to birth. The one's that do are born with physical anomalies and multiple organ failure and usually die within a few months.
http://www.chclibrary.org/micromed/00046360.html
At least with the amnio she will be given a definate diagnosis. I do appreciate how worrying it is going through the same myself and been given such bad odds. I'm holding on to the fact that even 1:4 which is considered very high risk there's still a 75% chance our baby will be ok.
I will think of your friend
Take care
Lolly X