Sorry - this is my first pregancy so I'm not very clued up on a lot of stuff. I had my dating scan and it put me at 12+5. But I KNOW that I conceived about two weeks later than that. Are they measuring from the date of my LMP or is the dating scan just.. accurate? I'm freaking out becuase my wonderful dad died a week after I conceived and (obviously without knowing I was pregnant!!) I had a couple of weeks of drinking and smoking much more than usual. I know that during the first three weeks the baby isn't much affected by what you do- but if they are saying somehow my dates are wrong then I'm terrified I might have done some serious harm in the most important stage. Please someone answer, I am driving myself crazy!