Iv just had a scan at 21 weeks asked to come for one early instead of 23 weeks because at the first scan they couldnt find any nasel bone, a sign of downs. Just had the 21 weeks scan but still no nasel bone all the other soft markers fine no other signs or problems. The sonographer said because of this i have to go back in 2 weeks for another. The chances have gone from 54in 1 chance of downs to 30 in 1 today, although i have already decided to have the baby what ever.but still worried.