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BIG difference in dates of intercourse and TVS ultrasound and LMP.?

(5 Posts)
R72485 Sun 28-Apr-13 17:12:50

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!

roofio87 Sun 28-Apr-13 17:44:36

all professionals date a pregnancy from the first day of your last period. so say you have you're period on the 1st of the month, and you then ovulate and have sex/conceive on the 14th and find out you are pregnant on the 28th you are classed as 4 weeks pregnant even though you really only conceived 2 weeks ago. so at ultrasound 4weeks after having sex they would say baby is 6 weeks. does that make sense?!

EuroShaggleton Sun 28-Apr-13 18:09:17

The dating isn't accurate early on. There can be huge variations in the estimated age based on size when you are looking at something that is only a couple of mm bit. And you have to consider what roofio said about dating. If she normally has a cycle a bit longer than 28 days, then you were probably bang on for her ovulation on 5 July and hit the jackpot first time.

brettgirl2 Sun 28-Apr-13 18:49:53

I didn't understand your post fully in all fairness. However, if you trust your girlfriend so little then your relationship is doomed anyway. I also hope to god she doesn't find this thread!

willitbe Tue 30-Apr-13 09:00:50

R72485 - I relpied in the other thread that you posted this question, but 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. On top of this, with early scans the tilt of the uterus can make a huge difference, for women with a retroverted uterus the early scan can be behind by 2 weeks, look at the misdiagnosed miscarriage website to see this happens frequently. Likewise if the uterus is tilted in the opposite direction, the scan can suggest that a pregnancy is further ahead than it really is, which is what was probably the situation in your partners case.

The only accurate time of dating a pregnancy is later 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.

Also, it does show that you have a real trust issue going on here with this woman. That doubt, has no foundation in reality in this situation, but that is just my opinion from what you have said.

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