Does anyone else think predicted due dates are completely wrong?

[Dawnybabe]

My midwife told me my due date is 40 weeks from the first day of my last period. That was 13th March, so my due date is today, 18th December. Which also means that my due date is exactly nine months from the last day of my period, 18th March. My beef is A) I certainly wasn't having sex on the last day of my period, yuk, B) Would there have even been an egg to conceive with, cos surely the last egg is still being disposed of at that point, and C) They say you're not fertile till after your period when the next egg is getting going, so by my reckoning, when we started trying again after my period, that would make my baby due any time between the 20th and the end of the month??? Going by the nine month timescale.
Somebody help me, my brain hurts (as does the rest of my bloody body by now).

no, the way a due date is calculated is, from the first day of your last period, add 9 months and 7 days, or 40 weeks. so while a pregnancy isn't technically 40 weeks, because you conceive during your fertile time, that's how it's predicted so that everyone is on the same calculation scale iykwim.

DD was due 15/05 and arrived 16/05. Not that much out tbh..!

I knew when ds was conceived down to a 24 hour window (either Christmas night or Boxing day night 2002 if you're interested) because it was the only period we had sex for a whole month! The mw didn't believe me and she also didn't believe me that my last period started on the date it did. They gave me 3 due dates, each varying by about a week, and ds was eventually born 2 hours and 18 minutes short of the first date I was told.

DS was due on the 18th December last year and he cam on 11th November at a perfectly healthy weight and fighting fit. They still had to keep him in for a week to to be sure but I am pretty sure the dates were wrong.

we had a mix up with ds1. our dates said mid april, their first date was end of march which after another scan tehy moved to 26th april. he was born on 25th april and MW tookone look at the placenta and said that he could have died if i had gone overdue as placenta was the state it would be had i gone over due by 3 or more weeks!!

With ds2 i agreed with eth dates and he was 4 days late

I know FLamey has issues with EDD's and huge differences with what she had and what they told her

I calculate that your due date is 20th December. I have always been told that you just add 7 days + 9 months onto the that date of your last period which would make you due on the 20th. All of the ready reckoners that they use do this.

Cheers nogoes. So is nine months accurate then? Cos it would still put me at well past christmas at this rate. Bloody hurts right now, I know that. I haven't ever had Braxton Hicks, I just get several hours of tight, hard, painful stomach muscles that feel like they're ripping apart every time I move. I hope to God the midwife does turn out to be vaguely accurate cos I really don't want another two weeks of this!
Thanks to everyone else too!

Bear in mind that you don't necessarily conceive when you had sex as sperm can live for up to a week. A more accurate way of working out your due date is if you know when you ovulated as conception will occur within 24 hours of this. You then add on 38 weeks from this date - however, this is still an estimate as babies are individuals and arrive when they're ready!

both mine were wrong. only had scans top go by both times and both dd and ds were born 'early' (dd by 4 days, ds by 2 weeks) but with classic symptoms of overdue babies. and i 'felt' overdue both times too

pink tinsel, thet is really interesting, with my 1st 2 i was dated by lmp, 1st dd was 11 days late, and 2nd dd was 6 days early.
This time i had been on depo jab, and periods hadn't returned so they dated me by scans at 5,7, and 11 weeks, I am due on saturday but feel really huge, bigger than either of my previous pregnancies, and the baby feels much bigger then the last 2 were at birth, both were 7lbs, midwife told me last wed this one was roughly 8lbs then, but going by the date they could leave me another 2 and a bit weeks! do you think scanning to find dates is innacurate??
Sorry to take over x

I had worked out ds to be due on 5th August using a ready reckoner; scans then put him as due on 31st July. I went into labour on the 31st and he was born on the 1st August - midwife's first comment was, "oh, how overdue was he?" as he had really wrinkly fingers and long nails! So who knows, maybe he was a little overcooked?!

lollipopz, i think the scans are wildly inaccurate, like miou's ds mine were both born with peeling skin, long nails, wrinkly fingers and with ds i was even asked by the midwife if he was overdue. i felt 'ready' well before my due dates too. of the 2 i think ds's dates were much further out as he was 2 weeks 'early' but 8lbs10ozs and very overdone loooking with him i had been bf-ing without my af returning so had no idea about dates. with dd the date the scans gave me was 2 weeks later than the date going by lmp, and although my periods are slightly irregular, not that much!

I know someone who had IVF (and no sex that month) so she really knew when her ds was conceived. The scan date she was given was 10 days earlier than when she thought he was due. She refused induction as she knew he wasn't overdue and he was born at 40 weeks + 20 days, looking just about right (although over 10lbs).

The earlier your scan is done, the more likely they are to be accurate. The ones at 5 and 7 weeks in particular should be pretty good at working out gestation, although they still have a margin or error of + or - 5 days. Did all three scans agree on dates?

I think one of the reasons the EDD is dated from the LMP is because (supposedly) we are more likely to remember that date, whereas date of conception can vary (ovulation times can suddenly vary, plus sperm can live in a warm environment for up to 5 days).

However, as another poster said, ds was conceived in the one and only night we tried that month, and arrived on his due date!

Not sure if this is said - you are only actually pregnant for 38 weeks. The first 2 weeks of the 40 (i.e 2 weeks from beginning of period to point of conception) you are not physically pregnant.

Dates have to be adjusted if you have a longer or shorter cycle.

Your MW will know what she isdoing when she calculates youe due date.