rostrum,
i also had a scare during my ds scan, mine was 1:64 risk and went thru counselling. but later blood test brought down the risk. like what gan said, for multiples bt may not be as accurate. the calculation is based on statistics, age, ivf etc...dun let it affect ur mood. go for second opinion at camden. u will be alright, dear. there has been many false alarm cases, just stay positive!!!