How did you calculate EDD?

posted 2 years ago in Pregnancy
  • poll: How are you calculating EDD?
    Based on LMP : (15 votes)
    63 %
    Based on O : (9 votes)
    38 %
    Based on something else : (0 votes)
  • Post # 2
    545 posts
    Busy bee
    • Wedding: November 2013

    Andthepupmakes3:  Unless you are super unsure of your O date, I think it makes much more sense to use the O date than LMP. LMP assumes an “average” cycle, so it assumed you ovulated on CD 14. I ovulate later (CD 21 this cycle), so estimating by LMP would put me a full week ahead of what I actually am, which can make a big difference early on!

    Post # 3
    2474 posts
    Buzzing bee
    • Wedding: October 2011

    Andthepupmakes3:  I just used my LMP. Since my cycle was between 26 and 30 days I figured it was close enough. Our 20 week anatomy scan had the baby measuring right on. My due date was July 24 and our son was born on July 18. Congrats to you!

    Post # 5
    3360 posts
    Sugar bee
    • Wedding: December 2011

    I used my O date – like Magpie86 said, if you know it, it’s more accurate than LMP.  Mine are only 4 days different, so it’s not a big deal, but O-date is generally the more accurate measurement to go by.

    Post # 6
    2696 posts
    Sugar bee
    • Wedding: June 2012

    Another vote for O-date (if you know when you ovulated). That’s the most accurate means of telling how far along you are.



    Post # 7
    7654 posts
    Bumble Beekeeper
    • Wedding: July 2012

    Andthepupmakes3:  I calculated by LMP because that is what my doctor went by, so I was always on the same page as they were when it came to talking about my baby.

    Post # 8
    2047 posts
    Buzzing bee
    • Wedding: August 2013

    Andthepupmakes3:  well I originally said my O date because I was tracking via FF and I O on CD19 (so 5 days after what would be counted by using LMP) It was a pretty obvious temp shift too.

    Anyways I had an ultrasound on what I had tracked at 8w1d from O…..thinking I might even measure less as it can possibly take a few days for everything to fertilize and implant. Based on LMP I should have been 8w6d….in the end I measured 8w4d lol…….sooo……closer to my LMP then O. The doctors are keeping my LMP as due date right now even though I have “proof” of my late O. Honestly you really wont know until you have your first dating U/S, cause you might get a surprise like me!

    Post # 9
    1805 posts
    Buzzing bee
    • Wedding: November 2012

    My doctor estimated by LMP even though I charted and knew my o date. They’ll generally stick with LMP unless you are over a week different in either direction in baby’s measurements.

    Post # 11
    3119 posts
    Sugar bee
    • Wedding: August 2012

    I used my O date originally, but my doctor ended up using LMP, so it was just easier to stick with that after I had my first appointment and u/s. The two were a few days off, and interestingly (and irritating to me because I loved charting and knowing O date), I measured exactly according to my LMP at my first ultrasound. 

    Congrats, and happy and healthy 9 months!

    Post # 12
    1140 posts
    Bumble bee
    • Wedding: September 2013 - Ontario, Canada

    I used my LMP as I was on a very regular cycle and that was what my doctor went by (I wasn’t charting though). At my 12 week dating scan it was confirmed as being one day later than estimated so so far it was pretty accurate. We’ll see if anything changes on Sep 1st when I have my anatomy scan.

    Post # 13
    140 posts
    Blushing bee
    • Wedding: November 2011

    I used my LMP because I know doctors normally use that to date your pregnancy. 

    Post # 14
    8480 posts
    Bumble Beekeeper
    • Wedding: September 2013

    They used LMP because I don’t chart and didn’t know my ovulation date.  We were way off, which they found out at an ultrasound and adjusted my due date.  O date would be more accurate because LMP assumes a “normal” cycle.  But in the end it won’t matter because it’s only an estimate anyway and baby will come when baby wants to come. 

    They will figure out if anything is too far off at an ultrasound and adjust.  I don’t think they will adjust at ultrasounds for only a few days difference though, I’m guessing it has to be a week or more.

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