give them a call!
when I went for my 12wk scan they said my water looked like I had a infection, made a big deal, didn't get told until I saw my midwife last week (16.5 weeks) and nothing was wrong, chase them if you are concerned, I hummed and harrdd abount having the downs bllod taken, but I am young and would keep the baby anyway but the hospital made a fuss saying if I had it done I would have to move my appointment forward as my scan due date was earlier than my actual due date, God they make it hard sometimes!