Im really nervous..what are the chances?

My husband and i have been TTC for 2 years and after a few cycles of chlomid we are pregnant! I have my first ultrasound today at 6 weeks 1 day. Im very nervous because my last pregnancy in 2009 ended in a blighted ovum and i don't think i can stand that heartache again, what are the chances this will be another blighted ovum?