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Explaining dates......

(20 Posts)
Everythinggettingbigger Thu 03-Dec-15 11:49:19

Hope somebody can help here, im slightly confused still and been trying to make sense of this.....

I don't know when I conceived, we were not trying and I was being careful.

when I went for my dating scan which, to my dates, would have been 12 weeks exactly to the day (based on the first day of my last period) they said I was 13 weeks......

does this just mean I ovulated really early after my period because technically the first 2 weeks you aren't really pregnant?

might seem a really silly question but baby brain....cant seem to get my head around it.

cloudjumper Thu 03-Dec-15 12:59:07

Your dating scan doesn't take into account your LMP, it determines how far along you are by the size of the baby. So it's very common that they add/take away up to a week from your calculations by LMP.

spilttheteaagain Thu 03-Dec-15 15:33:50

Yes it could mean that you ovulate early in your cycle. The standard model of 28 day cycle, ov on day 14 is certainly not true for a great many of us. Also bear in mind scans have a margin of error, usually quoted as + or - 5 days.

GoApeShit Thu 03-Dec-15 15:44:19

It's called a 'dating' scan because it dates your pregnancy using the size of the baby. Your previous 'dates' go out the window.

I was also put forward a week at mine.

Cantbelieveit1 Thu 03-Dec-15 15:46:10

I've not idea when my LMP started as I was told I couldn't have children so therefore never paid attention to it!

I have my dating scan next week and am expecting anywhere between 10-14 weeks!!

Everythinggettingbigger Thu 03-Dec-15 15:53:41

I get it's called a "dating" scan and I know they go on the size of the baby, my confusion came from having a period 12 weeks prior when they dated me at 13.

thanks for the replies. split I think you are right I must have ovulated very early in my cycle.

GoApeShit Thu 03-Dec-15 16:19:47

That just goes to prove medicine still has not developed a completely accurate way of measuring babies in the womb. I don't even know why we bother with due dates. Load of bollocks.

LibrariesgaveusP0wer Thu 03-Dec-15 17:37:32

my confusion came from having a period 12 weeks prior when they dated me at 13.

Sorry if this is stating the obvious, but if they date you at 12 weeks, it means that your last period was 12 weeks ago and the foetus is 10 weeks old, having been conceived two weeks into your cycle.

If they dated you at 13 weeks, the foetus is 11 weeks old and was conceived one week into your cycle.

It's also worth bearing in mind that they are measuring something very teeny that can vary a lot. I was put ahead a week when I knew it was physically impossible.

The dates can change by a few days (it changed by nearly a week in my case) due to ovulation date. This is assumed to be 14 days after LMP started, whereas I knew very well that I'd ovulated at 9 days on the month I got pregnant (short cycle). I also knew exactly when DH & I had had sex, which they didn't!

Whoknewitcouldbeso Thu 03-Dec-15 17:45:08

Sometimes they change you dates again at the 20 week scan. It's not an exact science, they are measuring your baby against an average. Unless you are worried about paternity I wouldn't overthink it. Just enjoy your pregnancy.

TheSecondViola Thu 03-Dec-15 17:49:33

The only bollocks is the people who take a due date as gospel and fix on one day out of a 4 week window. No scientist ever said it was as accurate as people treat it, your due date is the mid point of the four weeks in which you should expect your baby to be born.

VagueIdeas Thu 03-Dec-15 17:55:06

I know exactly when I conceived baby #2. I was using ovulation strips and we only had sex once that month.

However, when I went for my 12 week scan they said he was a week ahead and therefore put my due date forward by a week. But I knew my dates weren't a week out, he was just on the bigger side.

I didn't mind the change of due date to be honest. I was having an elective section and was crippled by SPD, so not having to wait an extra week was brilliant.

GoApeShit Thu 03-Dec-15 19:03:27

thesecondviola Pregnant women are very rarely led to believe anything different than it is one single date.

Everythinggettingbigger Fri 04-Dec-15 08:52:37

Thesecondviola, I am not naïve, I know the chances of me having my baby on this date are very, very slim.

Thanks power perfect explanation.

Vague I'm not complaining, its one less week grin don't get me wrong I love being pregnant, but I have very strong reasons to want to avoid a certain date in June and hopefully this will mean I wont go as far as that anyway!

thanks for your comments everyone.

My date was changed by 2 days with my DS, I actually went into labour in the morning of the first date I was given! (however he was not born until nearly 3 days later!)

TheSecondViola Fri 04-Dec-15 13:02:37

thesecondviola Pregnant women are very rarely led to believe anything different than it is one single date.

Nonsense. Babies are born all around us every day. Very few of them on their actual due date. If you've failed to notice that throughout your whole life thats your own fault. Nobody has led you to believe any such thing.

EDD: ESTIMATED date delivery. You do know what estimate means?

Junosmum Fri 04-Dec-15 14:48:34

They dated me at 13 weeks when I couldn't possibly have been more than 12 exactly (due to timing of DTD, we only did it once that cycle) so it just goes off size of baby. I wouldn't worry too much though, baby will come when it's ready!

Whoknewitcouldbeso Fri 04-Dec-15 15:43:28

It's worth saying though that midwives can get quite twitchy about induction nowadays so if your due date is out by a week or so that could mean you could start bring pressured to have a sweep when actually baby hasn't gone overdue at all.

Whoknewitcouldbeso Fri 04-Dec-15 15:44:06

There should have been some punctuation there somewhere 😳

LibrariesgaveusP0wer Fri 04-Dec-15 15:59:25

Whoknewitcouldbeso - That is pretty much exactly what almost happened to me.

I had had two babies, each 8 days over. On my third, I was put forward 8 days, despite knowing that anything more than 5 was impossible (but 5 seemed reasonably likely). I complained on the day. I made them write it in my notes.

It was only because I'd kicked up such a fuss then that I wasn't put under massive pressure to induce me. I went as far as +13. Thankfully my very supportive midwife agreed with me that I had predicted exactly this scenario and that I wasn't happy with induction until I felt it was biologically possible to be at +14. The fact that I had gone to 8 days over twice before and the fact that I had been clear from 12 weeks really went in my favour. He popped out at officially +13, which was +8 by my earliest possible due date!

Dixiechick17 Fri 04-Dec-15 16:12:36

I was also measursed at 13 weeks when I knew the date we conceived and knew I was only 12. I actually popped on what would have been my due date by my actual dates and not by the dates on the scan smile

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