Going by LMP or by "O" date?

Is everyone going by LMP as far as their EDD is concerned? I know when I "O", but my doctor still wants to go by a different due date.

The thing is, is that I found a very, very small blood clot when I wiped so I went in today for an ultrasound. The baby looked great, they can't find the reason why. Going by my ovulation date I am 11w5d. Now if I go by my LMP I'd be 12w0d today. Well, the baby measured a week ahead which would be 12w5d if I was 11w5d today, and my EDD has been 9/22. Well, she wants to go by a 9/20 EDD, but she put me at 12w2d now??? I don't understand? I didn't get to calculate it until I got back to work, but I didn't even ovulate then? I'd hate to call my OB/GYN just to ask this question. She said I can go by the 9/22 EDD if I want, but she's going by 9/20. If my EDD is 9/20 that would be my LMP which would make me 12w0d. I have no idea where she got the 12w2d from? Any ideas? What do you girls think? HELP... I'm so confused now!!! Thanks!

Re: Going by LMP or by "O" date?

Its only really 2 days so I wouldnt worry about it to much. Those U/S's can be off a few days, which is obvious in your case.
I would however go by your doctors EDD so that your both on the same page for if your late, when your late and things like that.

Re: Going by LMP or by "O" date?

I too had all these problems with my EDD regarding my LMP, my "O" date, and the size the baby was measuring. Since it is only a matter of 2 days for you (the same as it was for me), I just use the EDD the doctor gave me. It really is only a window anyway, not an exact science.

Re: Going by LMP or by "O" date?

Thanks for the replies!

My concern really is, is that if I go by the EDD that she wants me too, than it's only a matter of 2 days, but if I go by how far along she says I am which was 12w2d, than it's a matter of 4 days?

I forgot to mention it, but the reason I'm so concerned is that she's having me come in 3 weeks from today to do the AFP test. Which if I go by her EDD I would be exactly 15w0d, but if I go by my ovulation date, I will only be 14w5d. So I don't mind going by her EDD, but when it comes to the AFP test it's suppose to be done between 15-18 weeks, right? So if technically I'm only 14w5d, won't the results not be accurate like they need to be? Would that much of a difference in days make that much of a difference in the results? I think 2-4 days can make a difference and if I'm technically not 15wks yet, it might come out wrong. Maybe I'm just confusing myself and worrying over nothing. What do you think? Thanks again!

Re: Going by LMP or by "O" date?

If your measuring ahead, thats a good thing, the bottom line is as long as your at least measuring at O date, it doesnt matter at all...

ETA- you can have AFP as early as 12 weeks...Although thats not standard practice....and as late as 20 weeks.

Message edited 3/8/2006 7:01:05 PM.