Ladies, before I possibly make a pillock of myself at the scan tomorrow, can I pick your brains on dating pregnancies? I am kind of expecting to be told my baby is "small" for dates, but actually I think my dating scan was about a week out.
As I understand it, actual pregnancy is 38 weeks from conception to birth? (to get to 40 weeks, they add 2 weeks that in theory takes you back to your period, assuming ovulation on day 14)
My dates were:
Period started: 31/05, lasted 5 days
Ovulated: 11/06, on CD12
Usually have 10 day luteal phase so was expecting next period on 21/06, got BFP on 24/06
So, counting forward 38 weeks (or 266 days) from ovulation (assuming conception was that day, or possibly the day after) gives an EDD of 04/03/2011.
This was the due date I originally worked out and hence why I am in the March group 
However my dating scan came up with EDD 25/02/2011, a whole week earlier, so I reckon there must be a margin of error/big baby??
To have an EDD of 25/02/2011 I would need to have conceived on 04/06, i.e. CD5 when I was still on my period. Surely this would be nonsense?
Do the NHS think you are talking out of your arse/clueless if you try to argue dates with them?