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Conception

When's the best time to get pregnant? Use our interactive ovulation calculator to work out when you're most fertile and most likely to conceive.

Original poster

how accurate in dating pregnancies are scans done at 8 weeks?

27 replies

sparklingreactions · 22/12/2008 19:49

how accurate in dating pregnancies are scans done at 8 weeks? could a scan at 8 weeks possibly have been an 11 week fetus and be out by 3-4 weeks. i had 3 scans and they all tied in to 4 days of eachother.

OP posts:
NAB3hundredChristmaslights · 22/12/2008 19:49

Mine was 1 day out.

Original poster
sparklingreactions · 22/12/2008 19:50

does anyone know if they can be as much as 3-4 weeks out at an early san?

OP posts:
yama · 22/12/2008 19:51

I'd say they are spot on. Before 15 or 16 weeks growth is very specific.

I had a scan at 8+5 and it was day perfect.

traceybath · 22/12/2008 19:52

i don't think they could be 3 or 4 weeks out at 8 weeks - the measurements are too small.

thats why most places like to do dating scans as close to 8 weeks as possible.

traceybath · 22/12/2008 19:53

if you thought you were 8 weeks and scan is saying 11-12 weeks i'd believe the scan - maybe you had a small bleed but not a proper period.

Original poster
sparklingreactions · 22/12/2008 19:55

all 3 scans showed that my lmp was the 3rd june will i have concieved about 2 weeks later than this date?

OP posts:
ib · 22/12/2008 19:56

Mine was spot on. I've been told that before 12 weeks they are accurate to within 3 days or so.

Original poster
sparklingreactions · 22/12/2008 19:56

no the scan was saying i was 8 weeks from my lmp but i my lmp would have been 9 weeks but i ave a long cycle could this b why they got it wrong bcos i didnt say i have a 35 day cycle?

OP posts:
ib · 22/12/2008 19:57

Did they not give you a conception date? They did with me, and my lmp was presumed 14 days before because I couldn't remember the actual date.

SleighGirl · 22/12/2008 19:58

the scan gives the age of the feotus completely ignoring the lmp.

Your lmp is probably less accurate than the scan date tbh

traceybath · 22/12/2008 20:01

your cycle length is irrelevant from the perspective of an early scan.

i had a scan on friday as have been bf and no periods - shows i was 7wks and 5 days.

i actually normally have a very short cycle - about 24 days which may contribute to the fact that i tend to have early babies (one at 39wks and one at 37 wks).

So is it just a week different from what you thought from your lmp? If so - you may have just ovulated later that cycle.

Lulumamaloveslatkes · 22/12/2008 20:02

you have posted lots of threads about this and seem inordinately worried your dates are wrong, but a month.

is there another underlying issue?

if you are concerned, you must discuss it with your MW

Original poster
sparklingreactions · 22/12/2008 20:03

i think i concieved on the 16th of june the scan showed my lmp was 2 weeks before the 18th of june on the 4th 40 weeks after this is my due date and 38 weeks from where i think i concieved is my due date shouldi just trust the scans?

OP posts:
walkinthewoods · 22/12/2008 20:04

My first scan at what would have been about 6wks dated it to 4 wks, but I knew this was impossible because I knew I had ovulated at a certain time and because of when I had had sex (iyswim) When I had my next scan at 9wks, it dated it exactly to my dates and I was vindicated ( I told the sonographer that she must be mistaken etc and that I was suffering morning sicknss etc, sh told me I must hav particularly high levels of pg hormone, and also I would have tested pos. a week after I was due, knew the scan was wrong)

traceybath · 22/12/2008 20:11

yes - trust the scan.

ib · 22/12/2008 20:12

If you had sex on the 16th and your scan says you conceived on the 18th there is no inconsistency at all - perfectly possible to conceive 2 days after sex, and within the 3 day margin of the scans.

Original poster
sparklingreactions · 22/12/2008 20:23

these are my dates do u think they are right or could i have concieved the month before what i thought was my period as my bump is huge haah ..

i had a period may 25th 08
i have a 35 day cycle
i had sex june 16t 08
had a scan that showed 8 weeks on july 30th (this put my period at a week later than it was but minus the 2 weeks before i concieved it pretty much went back to the day i concieved)
had a 2nd scan that showed 13+1 (4 days less that the 1st scan showed they took my due date of 15th march 09 from this)
then 3rd scan at 21 weeks(tied in exactly with the 1st scan)
my due date is march 14

OP posts:
hannahlouhoo · 22/12/2008 20:25

My due date was taken from early scan date given, he was born on due date!!! i'd trust the scan tbh!!!

Original poster
sparklingreactions · 22/12/2008 20:28

yeah i think i will the 2nd scan i was given which my due date was taken from put me about 4 days less than i think i am but 4 days is nothing im sure my little jelly bean will come when he or she is ready anyway haha xx

OP posts:
ste280380 · 16/04/2011 23:17

i had sex with my gf on 18th dec and 31st dec but when we went for scan on 23rd march it said she was 12 weeks 4 days or 12 weeks 5 days..which takes it back 2 xmas eve or xmas day...does this mean she cheated

BikeRunSki · 16/04/2011 23:19

Mine was 10 days out.
Had 12 weeks scan this week which agrees with my dates perfectly.

BooBooGlass · 16/04/2011 23:22

Oh yes ste without a doubt Hmm
Sperm can live for quite some time, and conception doesn't occur immediately. WHy on earth would you count back the days to see if she was cheating? Sounds like a nice trusting relationship you've got there

Ilovekittyelise · 17/04/2011 21:25

the 12 weeks and 5 days is from the date of the beginning of the last period. so she started her last period on dec 24 (by my back counting) so she must have conceived anytime from about 1 to 3 weeks after that, depending on the length of her cycle. i must admit i think its pretty vile that you are questioning her fidelity at this time, but felt compelled to correct your mistaken understanding of the dating of a pregnancy in case you are actually using this as a basis for an accusation.

Riri01 · 05/10/2013 10:32

I had a scan it was dated at 9wks 3 days, i slept with another person other than my partner an this was on 17aug that would make it 7 wks can they be wrong by two wks? Pls help as this will determine if i have it

Totesamazeballs · 05/10/2013 11:14

Your pregnancy is dated from the first day of your last period, not from when you think you conceived/ slept with this other person. So count from when your last period started.

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