so confused about calculating due date

so my lmp was march 26th. i was charting my bbt and it looked like i O'ed on april 6th.

when i go to random online due date calculators, they say my due date (by date of ovulation) would be dec. 28th.

but when i saw my midwife, she said my due date would be jan. 1st.

i guess she is going by my lmp, but i don't understand why if ovulation date seems like its more accurate? (i o'ed on day 12 of my cycle, not the 'standard' 14)

i know i am making a fuss of just a few days, but i just don't get how it's normally calculated.

what would you say my due date is???

Re: so confused about calculating due date

so funny because with DS my lmp was March 26th, his due date was Jan 1st and he was born on Jan 1st! I argued too because I knew when I ovulated but they always go by your LMP.

Re: so confused about calculating due date

most dr.'s go by your lmp so I would just go by your lmp

Re: so confused about calculating due date

Yeah it is very confusing. I had just had surgery a month before down there, so my period was all messed up. I started out being due July 12th when I first went to the doctor, but I knew that was way wrong b/c of when I O'ed. Now I am due July 6th and have been for the last 20 weeks.

Go Figure...for me LMP had nothing to do with my due date. I was right all along. I said July 6th from the get go, shows that we do pay attention to our bodies and our schedules.

Re: so confused about calculating due date

Re: so confused about calculating due date

still unsure why they all go by lmp instead of o date, but i guess they know what they're doing!

well if i have to go by lmp, then a new year's baby it is!!! thanks

Re: so confused about calculating due date

For some reason, the doctors base everything on a 28 day cycle, even if you tell them otherwise.

I figured I am due on May 16th because I know when I O'd, but originally the doctor I first saw told me May 13th...but the sono determined May 18th. So they have May 18th in my chart now after picking every date in the teens-literally.

It really is just a guideline, you can go 2 weeks before or 2 weeks after.

Re: so confused about calculating due date

There was a post about this last week. When you O the egg doesn't get fertilized and implanted right away so that's why they don't go by your O date.

I'd rather Jan 1st than Dec. 28th anyway! Baby New Year!!

Re: so confused about calculating due date

my LMP was 3/26. I know I O'd on 4/9 since I have monitored cycles with an RE. Tentatively, that would make 12/31 exactly 40 weeks. Im sure it can go either way though by a few days.

Re: so confused about calculating due date

I'm curious to know what my doc will say.
My LMP was March 18 and I O'd on April 8th!
He's having me come in on friday when I'll only be 5w1d. I'm pretty sure he's figuring that I'm 6w.

Re: so confused about calculating due date

They will go by your LMP and then the sonogram. I O'ed early (CD 11) the month we conceived. At first, by the LMP, they said August 16th, but after the early sonograms, they changed it to August 12th.

Re: so confused about calculating due date

I think one of the reasons why they go by LMP and not when you Ovulated is they know you are giving an accurate date for LMP. Not many women really know the exact date the ovulated. even ovulation predictor tests can be a bit off. When they do the first sono, they will typically adjust the date if it is more then a day or two different. Also if the baby is constantly measuring behind or ahead, they will adjust accordingly.