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Anyone know if 41/2 wk gestation at scan is from lmp or from conception ? Need some reassurance please .

(16 Posts)
fakeblondie Fri 23-Oct-09 21:18:26

Ok here goes.
Had mirena out 1 sep.
Had af 7 sep until 12 sep .
Had unprotected si lots of times on and after 26 sep .
Had what i thought was af sat 10 oct but so slight did preg test 12 oct - was initailly neg but when i went back to it was positive.

Lots of pos tests since .
Went for tv scan today as had hyperemesis with last pregnacies and just didnt feel pregnant .

They saw a 4.6 mm sac with a good ring around it .
No yolk sac as yet so took hcg blood test .
Going for repeat blood to check that hcg going up sun morning and have to ring for results monday .

They said i am 4 1/2 weeks .
So either something is up or i am just panicking and really only 4 1/2 weeks and pregnacy testing has just got so good since i last needed one !

I thought af was due about 5th oct which would make me now about 6 weeks not 4 1/2 .
However i actually only had sex on 26 th sep which is less than a month ago , so if they are measuring this from conception it would all fit in .
Sorry to harp on but you guys seem so up to scratch i thought someone might know x

whomovedmychocolate Fri 23-Oct-09 21:19:28

From LMP. Stop worrying!


fakeblondie Fri 23-Oct-09 21:49:53

Ok x

Georgimama Fri 23-Oct-09 21:51:41

4.6mm sounds about right for 4.5 weeks - I had a scan at 6 weeks and DS (now nearly 3) was only about 5 mm then.

Congratulations btw.

fakeblondie Fri 23-Oct-09 21:55:50

But i thought i was 6 weeks if i go from my lmp ? y lmp was 6 weeks ago but i only had sex on 26 sep which is 4 ish weeks ago . x

EldonAve Fri 23-Oct-09 21:59:08

it is from LMP

Georgimama Fri 23-Oct-09 22:02:27

How old are you? You may have ovulated again later in your cycle. A friend of my SIL's (aged 37) has twins who were conceived separately - when she had an early scan one was noticeably larger than the other (and no deformities) and the obstetrician she saw about it said that was the only way it could have happened. He thought about ten days apart.

fakeblondie Fri 23-Oct-09 22:14:50

38! x

Georgimama Fri 23-Oct-09 22:32:21

Could have been that then (late ovulation I mean)! Hope bloods are OK. x

fakeblondie Sat 24-Oct-09 12:32:25

my hcg was 4524 ?

ShowOfHands Sat 24-Oct-09 12:48:58

HCG varies wildly from person to person, there's a massive spectrum of normal.

Early scans are very difficult before the foetus is properly developing and measurable.

Try not to worry. You don't know when you ovulated, the scan might not be desperately accurate. A positive pg test, a developing sac, rising hcg levels and no bleeding are what you expect atm.

EdgarAllenPoo Sat 24-Oct-09 12:54:58

from lmp - but don't worry about it to much. there is a +- 10 day margin of error for scan dating (best at 10 wks) but that is still better accuracy than dating from LMP.

R72485 Sun 28-Apr-13 17:10:17

Hello All.

I might sound, and I do, like a suspicious MCP but I am curious.

Our Timeline.

1. Her LMP was on 14th June.
2. She moved in with me 2nd July.
3. We had OUR first penetrative sex on 5th July and showered together, without Condom (no penetrative sex) on 7th July. I did ejaculate over her while the shower was running.
4. She missed her Periods on nearly 16th, thinking that this is the normal range (5-6 days) of delay that she goes through.
5. The Strip showed POSITIVE on 22nd July.
6. We got a TVS U/S got done on 26th July, saying the GS to be 5 weeks 4 days old. Sac 3.3 GS 13.9 mm.

But, considering the move in and the 'unprotected' shower, 2 weeks and 4 days have passed between the 'unprotected' contact and the Ultrasound.

However, if we DO start the counting from her LMP, it is, indeed, 5 weeks and 5 days!!!

What's wrong, where? Who?

I know this is confusing, however, so am I!

She says that she hadn't had sex with anyone else, for months, before moving in with me.

Am I worrying too much?

We got a medicated abortion, anyway.

But this vast difference in dates has made me curious.

Very curious!

AND Concerned,

One creeping doubt!!!

The Ultrasonologist did not know her LMP.

He gave the date based on the sac size, Sac 3.3 GS 13.9 mm!

Which gives?


PS. I know that I should carry on but I want to clear this one. It is, though, not haunting me, still it troubles. Hope you understand!

PuppyMummy Mon 29-Apr-13 06:58:40

I have no idea but you might be better posting in relationships or pregnancy.

there are a lot of ladies desperate to conceive here and your comment comes across as quite flippant.

willitbe Mon 29-Apr-13 17:37:56

R72485 - in answer to your question:

Assuming the scan is accurate, which to be honest it is not at this stage, it can be out by up to two weeks, so you are starting wrong here to start with, but assuming the scan date is accurate:

26th July - 5weeks 4 days
Then assumed LMP is 17th June.
Assumed date of ovulation is 1st July, conception occuring within 48 hours of this at the latest, thus 3rd July.

BUT and a huge but, the scan dates are not reliable in very early or late pregnancy. So it is perfectly believable that the scan date was out by at least a week, so this would give the assumed conception date at 7th July.

"Ultrasound dating of conception is not reliable for determining paternity because the ultrasound can be off by at least 5-7 days in early pregnancy." from

"How accurate is pregnancy dating?: A dating ultrasound of the length of the embryo when performed at 7-11 weeks gestation is accurate to within about 3 days. Beyond this time the accuracy reduces due to flexion (bending) of the fetus and individual growth variance." from

I could go and find you more scientific articles on the lack of accuracy of very early scans, but I am not sure that is what you are looking for. Basically dating a pregnancy from the sac size is inaccurate. The sonographer is measuring things that are only millimeters in length, and so only a very slight mis-measurement can cause a huge difference in dating.

The only accurate time of dating a pregnancy is in the first trimester when the Crown to Rump length (CRL) can be measured, as the scan that your partner had was so early the CRL could not be measured as such the scan dating would be inaccurate. Having had many early scans myself, I know that it can be out quite dramatically.

It all seems a mute point as you medically terminated the pregnancy, but it does show that you have a real trust issue going on here with this woman. That it seems is not justifiable, but that is my opinion.

R72485 Thu 02-May-13 05:56:04

Sorry, PuppyMummy, if it offended you. The intention was not to be flippant.

Thanks a tonne, WillItBe for your explanation. Yes, the trust issue was there. Long story, this is not the place. Thanks, once again.

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