dating scan question

[Mike]

hi all.

this might seem a stupid question and im sorry if it is but the hell with it.

first scan date is on 10th October, and as its a dating scan i just thought something about it.
you all know that you calculate how many weeks you are by counting back to first day of last cycle, which in my wifes case would make her 10 weeks, but most pregnancy happens about 14 after that first day, so when they do the scan and calculate the size of baby and tell you your exact date your due, does that officaily chance how many weeks you are.

for instance my wife is 10 weeks. first day of last cycle was on 18th july (or was it june........cant remember, lol) anyway 18th of something, lol, when we have the scan and if they say the baby was conceived 2 weeks later, then would the pregnancy weeks drop 2 weeks to 8????


im kinda starting to confuse myself trying to explain this, but hopefully you get the jist of what im asking.

 

[cherelle]

i dont think the weeks drop, i think its always classed from the first day of your last period x

 

[Mike]

thats what i was thinking. just wanted conformation.

thanks x

 

[Lacey's Mummy]

Just like what cherelle said, it's still classed by period. The dates don't normally change by more than afew days!

 

[pinkymum]

Thanks for asking this Mike, I was wondering the same thing lol

x x x x

 

[MrsR]

Just to throw a spanner in here but they changed my due date after my daring scan by 5 days. So before the scan they were saying I was due on the 8th October and after my scan they changed the date to the 13th October as baby was measuring 5 days smaller than lmp dates put it at x

 

[MrsR]

Dating scan not daring scan-stupid iPhone!

 

[smess26]

Mike is your wife due on the 24th April my last period was the 18th July.

I also don't have a clue why the date changes or not?!

 

[treeze]

i am no expert but i think that the date you give as the 1st day of your last period is what you go by to begin with. they count exactly 40 weeks forward from this date and that is your due date. If you are confident that your dates are right (which i'm sure most of us on here are!LOL) then when you have the scan it probably won't change much...

The only thing that nobody can ever be certain of is when conception actually occurred which could be up to 5 days (how long the longest sperm can live for) either side of when you know you tried to conceive. So this maybe could alter the "age" of the baby by up to 5 days? I think? For some people conception might have happened within a few hours of trying but others it might have been a few days later (hence making the baby a few days younger than thought?)

also surely it must make a difference as to when you ovulated - if one person ovulates on cycle day 14 but someone else ovulates on cycle day 21 (which we all know is different for each of us) then surely that makes a difference to if you only count from the first day of your last period?

So at the scan they "date" the baby based on specific measurements taken of the baby on the day of the scan (you see them putting little markers on the screen) and this will then tell them based on figures how old the baby is and hence when it will be due.

Some people don't really have a clue when their last period was so i think this is when there can be a big difference between what they think/guess their last period date was and when it actually was.

i found quite an interesting webpage about it all too:

http://www.baby2see.com/medical/nuchal_12weekscan.html

oh well - don't know if that's any help or not!!!! treeze x x

 

[Emmamb]

Basically in a womans cycle ovulation happens at different times and so does implantation/conception. Due date is caculated from conception + 2 weeks. Which is y even wen ur certain of dates it can still change...I got put forward 3 days which means I must have ovulated earlier in my cycle than 'usual' xxx

 

[Mike]

Mike is your wife due on the 24th April my last period was the 18th July.

I also don't have a clue why the date changes or not?!

no 20th april, its becuase she has a short cycle according to cycle, but my wife is late for everything so most likely 24th, lol, dont tell her i said so. i be in the dog house till the baby here. lol

 

[Mike]

ok so basicly it might be a case of when we got to the scan at 12 weeks, theres a chance we cold be knocked back to 10 weeks for example???? or do they just carry on from 12 weeks????

 

[Emmamb]

ok so basicly it might be a case of when we got to the scan at 12 weeks, theres a chance we cold be knocked back to 10 weeks for example???? or do they just carry on from 12 weeks????

It's unlikely ul get put back a fortnight,possibly forward or back a few days,especially wiv ur wifes short cycle xx

 

[sarl1967]

It can depend as Emma says on the Ovalation too - i knew i ovalated early so was convinced i was between 3 and just 1 day different on my dates as to what doc was giving me - so when went for dating scan wasnt surprised that they but us forward 2 days x

 

[ShadowWolf]

I got put back a week when I went for mine, we had a rough date worked out from my LMP but I have no idea of when I ovulate so obviously I was slightly late.... i think... :S

xxx

 

[midnight]

just my pennies worth theygo by the date the scan gives not by your lmp date so yes there is a chance your dates will change