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Thread: Does the length of your cycle make a difference to your EDD?

  1. #1

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    Question Does the length of your cycle make a difference to your EDD?

    I was just wondering, when I fell pg my cycles was about 35 days (from memory). I am pretty sure I would still O about 14 days before AF arrived. But the time between AF & O was longer then the 14-16 day average.
    I worked out my EDD as the 28th of Oct. But the midwife said going off my LMP date my EDD is the 22nd. Then a dating u/s at what I though to be 11 weeks, made me 12 weeks & EDD as the 23rd.
    So does the lenght of your cycle make a differnece to your EDD? ONly reason I ask is I am due on monday & I know its very possible to go over due anyway, But do you think I should expect to go over? At least to the 28th anyway?


  2. #2

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    Yup, makes a difference. You're 2w pg when you O, which is usually 2w from LMP (if you believe the doctors). If you're 2w pg and 3w from LMP then you're still 2w pg, not 3w.

    My hospital didn't listen about my irregular periods either and insist on dating me from LMP (so EDD of 31.01) even though all the early measurements confirm 03.02 - I'm amazed I O'd that early and refuse to give out an EDD as I'm sure I'll go over! My cycles were 32-55 days, usually about 6 weeks in length, so it's daft to just go from LMP and ignore the scan data, especially from early scans.

  3. #3

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    Well the early scan said the 23rd so......

  4. #4

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    I agree that the length of the cycle does make a difference - but only if you O later in the month. If you still O around the 14th cycle day then the standard calculation should be right. But if you're like one of my friends who doesn't O until more like day 20 - it makes a big difference!

    HTH

    Love MG

  5. #5

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    Do you know when you O'd, FJ? I didn't know, so the scan was a big help. If you do know, you can get a more exact EDD - this could have been a 4-week cycle that your body gave you just to be confusing.

    If the baby is spot on average for the 23rd then go with that, if it was "small for dates" (babies are very, very average in the first trimester) then go with the 28th.

  6. #6

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    My OB went by my O day.. since I gave him a printout of my FF chart. hehe.

  7. #7

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    I would be able to tell you exactly but when we had to reformat the puter I lost all that. My last AF was the 15th of Jan. My cycles where getting shorter & shorter. As AF had only returned the October before. Later scans I have had the u/s guy did say she was small, but not too small for the date. But the dating scan said the 23rd. I am happy to go with that I just don't want to have the midwife say I need to be induced because I am overdue at my next appointment(26th) if there is that chance I am not due untill the 28th. I am happy to stay pg for as long as it takes for this little firl to come on her own. I am lucky that I am not over it as such yet. So I wont be agreeing to any inductions etc unless there is a concern for my baby.

  8. #8

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    I think it would make a difference if you O later than day 14.
    My LMP was 3/6 so the hospital told me 10/3/07 for our EDD.
    I O'd on day 19, and when I had my scan I was measuring 4 days smaller than what the LMP date would have been. Only a small diffrence, but still a difference.
    I read somewhere that you should count 38 weeks from the day you O to get an EDD, if you dont O on 14.

  9. #9

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    Well I think I o'd on the 30th of Jan & counting 38 weeks from then gives me the 23rd of Oct.

    Well I will expect anything to happen from now & refuse anything to made to happen unless baby is at risk.

  10. #10

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    Fiona... I just noticed you have gone with the name Isla...I love the name...yay and good luck in the next few days..never know huh

  11. #11

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    I usually O on day 30-35, so my LMP dates were way off. The doctor wouldn't change my EDD though, until she saw the ultrasound results, which confirmed what I had said. I honestly don't understand why they assume that every woman has a 28 day cycle, and O's on the 14th day. There are LOTS of women who don't. They should ask the usual cycle length, and go from there.
    Even though I knew that I was two and a half weeks behind what the doctor was saying, it was still depressing to have to "do over" some of my weeks, after the ultrasound.
    But, keep in mind too, as you come close to your EDD, that there is a wide range of normal for a term baby - 37-42 weeks, right? So it doesn't make so much difference anyways. Hope the last weeks don't drag on too badly for you!
    All the best!

  12. #12
    *Beccy* Guest

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    Fiona ~ Go by your earliest scan EDD. The midwife at the hospital said that in the first few weeks of conception things happen at exactly the same time for each woman. Heartbeat starts at a certain time etc etc...that would be your best gage of EDD!

    When you get to your 18-20wk scan, the baby takes on genetics and it can give you a wrong EDD because some people are tall, fat, short, skinny etc.....

    Hope that helps???

    Beccy

  13. #13

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    I have a 28d cycle (not 100% when I O though) and I went 2 weeks late last time..... Sorry to be the bearer of bad news! So its probably not related to cycle length but O date as the others have said.
    According to my dates I'm 2d ahead of my scan dates based on their measurements, so pretty close.

  14. #14
    Kirsty77 Guest

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    Its definitely related to when you Ovulated rather then cycle length as my cycles were 7 weeks long when I concieved this bub! Geez I'd have ages to go then! I'd probably be due in december!LOL!

  15. #15

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    Yep - i didn't o til CD26 so i told my Dr i knew i wouldn't be as far as my LMP suggested i was. According to my u/s my calculations were correct!

  16. #16

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    Good Morning Ladies!
    My Ob is going by my scan dates because my LMP was 23rd March which gave my an EDD of 28th Jan, but according to my scans, my EDD is 14th Feb! Just over two weeks difference! I've had three scans that all confirm the same date. And yes, I have a very irregular cycle, it ranges from 30-60 days, but we still managed to hit the jackpot!

    Take care,
    Jess

    Me 26
    DH 25
    Bub #1 Due 14th Feb '07- A Valentines Baby!

  17. #17
    Percy Guest

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    I didn't ovulate until CD26 on the cycle I fell pregnant (ruddy PCOS!) so originally the dr put my due date according to my LMP which was mid January! I knew it was wrong and told him so but he wouldn't be budged! Anyways I was proved right - spot on actually - with the ultrasounds!

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