Working out your due date - irregular periods

Hi folks,

Just a general question. My periods were usually in between 35 & 42 days.

My last period began on the 15th November. We dtd 26th & 28th November and 3rd December.

Any online apps tell me I am due 22nd Aug (my GP said same) but at my private scan Dr reckoned I was a week behind that and guessed 29th Aug (he couldnt measure as the machine was playing up). I am assuming thats probably correct with my longer cycle periods - no apps seem to allow for them.

I know my 12 week scan will tell more (or I have my booking in at midwife on Thursday, maybe I'll know more then?) but i am just wondering in between times.

So at the minute Im either in my 10th or 11th week. I rang about my scan and receptionist said it gets processed after the midwife booking in so I doubt I will get it when I am actually 12 weeks. Getting very impatient!! lol


  • Some of the websites do take into account different length of periods, but you need to know exactly how long it was really for it to work.  

    Both times I've known exactly when I ov'd so could work out due date from that, and although everyone else went on the lmp date, when I had my first early scan with C that then agreed to my dates.  Fortunately this time I had a perfect 4 week period!  That's never happened to me before!!

    Don't worry too much about the scan because it would only mean you might be a week early, and if they're doing the Nuchal they'll redo if you're not within the correct dates (between 11 weeks and 13+6 IIRC)

  • I agree with deedee, I would go with the furthest pregnant you could be (so from your last period) then if you get put back you can still have screening tests etc later

  • I didn't know when my son was conceived so they used my 12w scan to date me. Even this time when I knew my period dates  they still used the dates from my 12w scan.

  • I really need to wait until my 12 week scan then dont I? Wish the measurement thingy had been working that day, wonder if I can ask for a discount considering lol.

    I am just getting really impatient and want to shout it from the rooftops!

  • I think from your dates of DTD, you probably ovulated relatively 'early', by that I mean based on your cycles being 35-42 days long. By a standard 28-day cycle, you would have ovulated on 29th November, so the first two DTD dates would have been within range, but even if your last DTD on 3rd December is the one that caught the egg (whilst baring in mind I know sperm can last 5 days) I think a week later is probably the latest you would have ovulated. So an EDD of somewhere between the LMP and the dates from your doc is probably right. All speculation of course! I'd go from the LMP anyway, as thats what they will all use until your dating scan, plus you get your scan at the earliest possible date that way! x

  • Im just a bit peeved as frenemy had announced her pregnancy the same week as 22nd Aug and she has had everything so far and I want all mine NOW lol

  • I had no idea on my dates as I hadn't had a period after coming off the pill a couple of months previously. I explained to my doctor who completely ignored me and made up his own EDD based on 'well you don't look like you have a bump yet.' Fortunately the receptionist at the hospital had more sense and called me because the referral letter was confusing and she decided to book me in a bit earlier. As it was I had my scan and they dated me as 12+1 so pretty spot on. If they'd listened to the doctor they wouldn't have booked my scan until I was 16 weeks!

  • Sasasi, what hospial are you going to? I had my scan at the first appointment although the letter didn't make clear that this would be the case.

  • Im in NI and the midwife booking in isnt at the 'real' local hospital if that makes sense?

    Receptionist said it would follow on from the midwife, she fills in the referral paperwork if that makes sense.

  • I thought you were in NI but wasn't sure whereabouts. I was at the Ulster but it seems very different depending of the hospital.
  • Ah! No I'm northern trust so I'm Antrim & midwife is at braid valley.  Ulster is a great hospital , I had my skin cancer operation there last month & I couldn't rate them highly enough. I work in Belfast though, if I'm still at work when labour begins I'll make them take me to the royal lol

  • I have ridiculously bizarre cycles and my LMP with E was 22nd October giving EDD 29th July. Had an early scan at what should've been 5+5 but there was nothing in the uterus but a fluid sac so I was a suspected ectopic. Long story short but that was ruled out and they gave me an EDD of 12th August. Fast forward to what was my 12 week scan and they made me 13+6 and put due date back to 29th July! Despite there being nothing in my uterus at the time he should've been there, which they put down to my long cycles.

    None of this would've mattered except surprise surprise I went post-dates and was induced at T+12 which was 10th August and E was born early hours of 11th August, a day before what I think was my actual due date! Had I been dated "correctly" in line with my cycles I could've had the homebirth I wanted, but all in all I had a really good labour/birth experience, it's just weird that with the dates they gave me he was actually still floating down my tubes!

  • I had a similar issue with this pregnancy where i had a period june 20th ...then another july 18th then a two week bleed begining of august. We were not trying but not being careful either....i only realised i was pg at the end of august where from my last bleed i was dated at 5 weeks. But i also was concerned due to odd periods and had told midwife to cut a long story short went for my 12 week scan to be told i was 18 weeks...
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