Iv had my first lot of blood (4 tubes) for the norm checking aneamia, blood group, hiv and the rest just wondered when they next take blood? Im 17 weeks. Do they take it at 20 weeks and do you know how much they take? Reason im asking is im terrified have to be prepared with lots of cups of tra and food as i faint when they take it. Dont want them surprising me and collapse on them lol x