Due date estimate- should I start to flag this up?

[Miffster]

All through the pregnancy I have worked off my last period date with the GP and midwives, however, I happen to know the 2 dates when I had sex with my DH (he was working away that month and only home for a few nights!) and they don't check out with the DD estimate of me ovulataing on day 14 of a 28 day cycle.

One posible conception date date was only 6 days after my period started, could we have concieved then? On day 6 of my cycle?

The other date was 20 days after my period began. In which case, I probably ovulated on around day 17/18 of my cycle rather than the standard day 14.

I don't know which one it was, but a clue may lie in the fact that due to a spotting/cramping scare, I had a very early scan and a strong flashing heartbeat was detected. At the time this was put down as being 6+1.

But I guess it could have been an older fetus - a full 8 days older, so the 6+1 fetus with the heartneat was in fact 7+2. It couldn't have been a 5 days younger fetus, could it? A heartbeat simply wouldn't show up at less than 6 weeks - it wouldn't appear on a fetus that was 5+3, would it??

Or would it? I am confused and can't get a definite answer off reading around.

I would really like to get some clarity because it affects my DD and could mean I end up being induced for being overdue when I'm not actually over due (and I have a horror of induction and want a home birth). It also affects whether I'm likely to have a baby over Christmas and when I start my mat leave.

So should I start flagging this up to my GP and the midwife?
I'm 27+6 now, according to my notes.
Or possibly 29+1.
Or maybe 27+1.

It's become this week's 3am-4am worry topic so am very grateful for your help!

Even if you had sex on day 6, doesn't mean you conceived on day 6, sperm hangs around sometimes lol, so it could have been nearer to day 14 (but not necessarily day 14)

If you flag it up I suspect they would err on the side of caution and put you at 29+1, which might mean you go 'overdue' when you're not.

What did your dating scan show at 12ish weeks?

I'd say it's theoretically possible you conceived on day 6 but marginally more likely that you ovulated late. That said it's unlikely there would be a heartbeat at 5+3 but then again I'm not a midwife. I just didn't want to say nothing.

True, what's the longest sperm can hang about?
And what's the earliest ovulatiom can occur in a cycle?

My cycle used to be 28 days but had been going awol for 3 months before I conceived, probably due to me doing a low-carb high protein diet and hardcore fitness regime (after 3 months of which I concieved very easily after 2 years of trying.)

I'm a bit confused. I thought you're due date was calculated 40 weeks from the first day of your last period so it wouldn't matter when in your cycle you conceived, you'd still have exactly the same due date.
Have I got this all completely wrong?!

Early scans are v accurate as the development in the first 12 weeks is fairly uniform. I'd take the 6+1 scan as being pretty close to your actual dates.

And you can refuse induction regardless.

Even if you question your dates I think they would be more likely to go on your dating scan and keep that as your EDD, just keep your own dates in mind as the time approaches. You could go anytime between 37 and 42 weeks and still be term.

saoirse, they calculate it from your period in the first instance so that they can give you your booking in/scan dates etc at approximately the right times. They then use the dates generated by the scan to adjust your due date.

Every woman has a different cycle. So some women will conceive on day 6 of their cycle, some on day 30 (two extremes I know). So that's over 3 weeks difference. Those two women have wildly different due dates and that's why you don't just use the first day of your last period to date.

Hiya miffster

I'm afraid that to the best of my non medical knowledge, there is an element of vagueness about these things because you may not know the date you ovulated on or how long the sperm lasdted for OR when the ball of cells implanted.

Early scans ARE supposed to be pretty accurate though- perhaps a few days out at the most.

What I can suggest is becoming zen-like about the due date as if induction is looming, nothing is likely to put off labour more than lots of anxiety.

I also have a phobia of induction and hospitals in general and have booked a home birth. I suggest reading up on your options re. refusing induction and whether you would consider that if all healthy and extra monitoring done?

Of course this is totally personal but if it helps my #3 was born at home at term +24.(had no idea of conception date though and noearly scan- late ones more inaccurate).

Dating scan at 12 weeks was 'fine for dates', est. fetal weight slightly under average, long legs and all other measurements slightly over average ( but DH is 6'3).

I suppose if I had sex on day 6 of cycle and the sperm hung about for say 4 days and I ovulated on day 10 not day 14, and got pregnant then I'm a few days further forward with the pregnancy than my notes say but it's not a big issue. And the 6+1 day heartbeat I saw would in fact have been about 6+5 or 6+6.

Whereas if I didn't get pregnant til later, on th esecond shagging occasion, the flashing heartbeat would have been that of a fetus concieved 24 days previously, which just does not sound very likely to me.

Did you have a scan between 10 and 13 weeks? If so, what EDD does that give you?

The "dating" scan between 10-13 weeks is very accurate and many hospitals now take the EDD from this. Earlier and later scans are not as accurate at setting the EDD. I would take your EDD from this scan.

Thanks for the replies, that is reassurring.

I think I will keep quiet and think that I am perhaps a few days further along then they think...in which case I get a few extra days induction-free grace.

:)

in my experience at my hosipal they only go by scan dates

I've just been checking NICE induction of labour guidelines as I am 41+1 with DC2 at the moment with no sign of imminent labour. In the guidelines it says that induction of labour should be offered based on the date from your dating scan, not the calculated date, as the dating scan is specific to the woman/foetus whereas the calculated dates are based on a generic menstrual cycle.

With both my pregnancies the calculated date based on 40 weeks of LMP was used only to roughly date the pregnancy for purposes of booking in. When the dating scan gave different gestational age, this was then the date that become my EDD. With DS it put my EDD 4 days later than calculated and with this DC it put my EDD 2 days earlier than calculated which actually coincides more with what I expected as my cycle is usually 25/26 days rather than the 'standard' 28.

They are planning my induction, should it be needed, based on the dating scan and yours would be too should you go that far.

As I understand it, sperm can hang around for up to 5 days waiting for an ovum to fertilise. So if you had sex with DH on day 6 of your cycle, you may not actually have conceived until day 11 which would put your EDD much closer to your scan date than the dates you had sex IYSWIM..

hi miffster AFAIK sperm can last about a week and still be viable - does that almost match up with your scan date? Scan dates seem to be pretty accurate - I was tracking my cycle and my scan date was w/in one day of when I thought I'd ovulated. I also don't think the egg lasts more than 12-24 hrs so your guess of oving on day 17/18 doesn't make sense with having had sex on day 20. You'd have had to ov'd closer to day 20 or later for that to have been the one!

Not sure if any of that helps! Seriously though, I think dating scans are really quite accurate.

I definitely know the dates when shagging occurred, but not the ovlation as my 28 day cycle had started going weird when I started low-carbing.

I had sex on day 6 - but if the sperm hung about for 5 days may well have concieved on day 11 of the cycle (or even day 12) Which is only 2-3 days out from the 14th standard day-of-cycle that the notes are using, based on last period. That would explain why the scans aren't disagreeing with the initial 28-day-cycle-based EDD. I guess a 2-3 disrecrepancy wouldn't show up, and it woudl explain why the fetal heartbeat showed at '6+1' - it was more likely, 6+3 or 6+4.
So induction-wise, I get a couple of days grace. Phew.

Hopefully I won't go overdue.Or come early, come to think of it. Any time from 37+2 to 40 weeks would be great, and avoid the poor baby having a birthday in the same week as Christmas - or worse still - the days straight after Christmas.

Hi miifster, I'm 25+6 today, but just wanted to say that in my experience early scans aren't as accurate as the 12wk dating scan. I had a scan when I thought I was 9wks pg, sonographer put me 9 days earlier(7+5), which I knew couldn't be right as I tested +ve on day 26 of my cycle (can't surely have got a +ve on the equivalent of day 17!), but the mw said they often catch up, and she was right as by my 12wk scan I was only measuring 2 days less and my 20wk scan I was spot on. But they have based my EDD on my 12wk scan, which is fine by me. They moved dd's date by 2 days aswell and she was born a week early anyway. Good luck with your pg!

I was born on New Year's Eve.

It is crap to be honest.

Im even mroe confused now.

Is it measured from ovulation or from when sperm meets egg, regardless of whether the egg has been hanging around for 48 hours previously before the sperm set off to meet up with it?

Could my 12 week scan be out by as much as 6 or 7 days and nobody have noticed? That sounds unlikely but could it be off by 3-4 days?

LMP began 9th March
Sex was 14 March (and also 28 March)

14 days after LMP gives 22/23 March as ovulation/conception date.

However, everything I have just read online seems to be saying that successful fertilising sperm tend to do the biz after a mere 48 hours - although they can go 5 days, this is v.rare. (It depends on the vaginal mucus environment apparently, which is affected by whereabouts in the cycle you are.)

Well, I know that sex occurred on the 14 March and I can't see how the sperm could live longer than 19th March. Therefore the egg was fertilised sometime between 14 and 19 March. That's day 6-11 of my cycle.

(Or else conception took place on day 20-21-22-or whatever of my cycle, but I can't see how that's possible when a fetal heartbeat was seen and a fetal age given of 6+1 weeks later on. And eggs don't hang around for that long, do they?)

I wish I'd paid more attention in biology classes.

If my poor baby is born on Boxing Day I will feel guilty forever.

Your baby will be born when it is born. You do not have to be induced.

Pregnancy is dated from 14 days before the sperm fertilised the egg. Or the average pregnancy lasts for 38 weeks from the moment of conception.

But a normal pregnancy also varies from woman to woman. Between 37-42 weeks is normal. So even if they know your exact second of conception, if their policy was induction from 40+10, and your body has pregnancies that naturally last for 42 weeks, then the question of induction will come up regardless.

The thing to do is to read up about expectant management, think about what circumstances would have to arise for you to consider induction and get on with enjoying your pregnancy. If your baby wants to come on boxing day, then so be it. It's probably quite nice in a lot of ways. Another party so close to Christmas, always off school, maybe some snow on the ground.

Christmas babies aren't so bad! Ds(7) was born 29th Dec- day before my 31st birthday. It won't scar him/her for life, honest!

And you could have avoided it, if it is an issue.

(When ttc both dd1 and 2 made sure was extra careful in march/april, lol- purely for financial reasons!!).

As for your edd- as someone has said anything from 37-42 weeks is considered term. Babies are very unpredictable little buggers! (unless you go for an elcs- but even then, they may surprise you!).

Congratulations- and try not to get too stressed about this- there are much bigger things to come !

Thanks I will try to stop worrying about it!
It's quite amazing what suddenly assumes epic importance during the middle of the night when pregnant!

I am quite comforted by the thought that I might be a few days further along than I think.
I will keep it as a nice comforting thought to myself and not tell the midwife. I am booked for a HB and they are fine about going 41+6 in my area so hopefully all should be good, especially as I have a couple of extra days to play with by my maths.

12 week scan is very accurate so I'd rely on the date from that if I were you!

And also remember you're not really overdue til after 42 weeks. Several women in my family had healthy babies after 42 weeks.

Miffster- i am 38 weeks- and spend my nights worrying about the Chilean Miners, the fact I haven't bought the right colour lightshade for the nursery,and packing and repacking my bag .. Insomnia is rubbish!!

a friend of mine got pg with a one night stand - so she knew the only date she had had sex to concieve - the hostprial told her she was worng but of course sperm hang aorund and wait a while - so they were both correct and niether wrong

I had ivf so I know within a few hours when sperm met egg! - but it doesn't matter, nobody has ever paid attention to that, because they never count from actual conception. Pg length is too variable anyway; '40 weeks since LMP' is just a guideline, as is the dating scan, but the latter will probably give you a closer estimate. The baby will come when it's ready, and if they want to induce you then make sure that there is a better reason than you being a few days over your estimated date, such as the baby is in distress or you just can't take it anymore.