FAB, I know it came from the best intentions but was just a wee bit too blunt for someone as sensitive as me. The registrar, doctor and midwife I saw today managed to convey the same message without being so harsh. Also, sorry to nit-pick, but you didn't actually say 'OC that goes undiagnosed' in your post, you just said 'if a woman has OC the baby could die'. There's a big difference beween those two claims. 
acatcalledfelix, if I were you, and was still worried about it, whcih you obviously are (and have a right to be!) I would go back into your assessment unit and explain and ask for another test. As FAB said, it can be dangerous if it is left undiagnosed and they are there to diagnose you after all!
snowball, thanks for that info. I need me some of those midwifery books. I am being very well managed so feel a lot better about it today.
Just to say that after today's visit, I am on vitamin K and urso, back in tomorrow for blood results and more monitoring, then we'll take it from there. If OC is confirmed they will induce at 37 weeks. Otherwise baby is BIG!! And wrt that problem, if I'm not induced at 37w, I will go back for a growth scan and depending on that outcome, will either be induced no later than 40w or else offered a caesarean.
Thanks for all the support, and felix, get yourself to hospital!