how can an US put your dates ahead if your certain on your LMP?

[ProudMum]

This was something I did not understand. My U/S put me 3 days ahead regardless of my LMP being spot on. How's this possible? AF wasnt early or anything but I did ovulate early- STILL ovulating early shouldnt make a difference to your dates if your LMP was right on time, should it? Im seeing the midwife today and she will ask my LMP- if she judges it by that then i'll only be 10weeks and 2 days when actually I'm 3 days infront. I just dont understand this at all. Should I take my scan report???? also i know if i do take my scan report, my nhs u/s wont be at 12 weeks, it'll be later basically because i've had a scan already.. so what does one do??

 

[mordino]

Same thing happened to me at my early scan yesterday. I am 6+4 weeks by LMP but my baby measured 7+1 weeks. She said I actually am 7+1 weeks!! We were rather surprised. It was the same consultant who looked after me in my previous pregnancies, so I didn't question her - I was just too happy that my baby's heartbeat was detected.

I know my monthly cycles very well so I will stick with my LMP for now - until my NT scan. I am just glad everything is going well so far.

I don't know maybe other ladies here would know?

 

[ProudMum]

I dont understand it one bit... I dont wanna be put back tho

 

[Crypto1976]

Because you may not have ovulated when you thought you did. A edd based on lmp is based on people with 28 day cycle who ovulate on cd14.

 

[ProudMum]

yes but even if conception took place on 21st/22nd for me... it would only make me 10 weeks and 2 days. I just looked it up.
If I ovulated early it still wouldnt put me 3 days ahead?? surely. My lmp came right on time...
I can see me getting put back again I hope not.

 

[Crypto1976]

I dont understand. edd is really more to do with when you ovulate rather than LMP, unless you have a 28 day cycle..... does it really matter anyway?!

 

[ProudMum]

I was only asking..

 

[beachlover1]

EDD has nothing to do with when your LMP was, some people have really long cycles. It is all based on the day you ovulated. Whats the point of going by LMP if you didnt ovulate til day 28 (like i did) the LMP would put me 2 weeks behind!! you would have ovulated early, then implantation would have been speedy. go by their dates, but remember....babies are hardly ever on time ;-)

The MW will go by your dates UNTIL a NHS dating scan is done...then they will adjust for all other scans. Dont worry!!
x

 

[mordino]

yes but even if conception took place on 21st/22nd for me... it would only make me 10 weeks and 2 days. I just looked it up.
If I ovulated early it still wouldnt put me 3 days ahead?? surely. My lmp came right on time...
I can see me getting put back again I hope not.

I can understand how you feel. With my daughter, her EDD was 9 January while others says 11 January! My waters broke on 20th and she was born in the next day. 10 days late!

So it was because of my experience that I didn't let it bother me too much as I'd learned that a very small percentage of babies born on EDD!

 

[holywoodmum]

if you ov'd early, then you'd conceive early.
But basically 3 days makes bugger all difference in the grand scheme of things!! your bubs will arrive when it's good and ready, be it 2 weeks, 1 week 'early' or a week orr two late.
if you want another scan then don't take US report...

 

[Rmar]

Your due date is 38 weeks after ovulation regardless of when your LMP is.

Also, in the first trimester a dating scan can be up to 7 days in inacuracy depending on which machine is used. The further along in the pregnancy, the more inacurate the dating scan becomes because babies grow at different weights and sizes. An ultrasound can be 500grams grams different each way than what the fetus.

Dating scans aren't necessary if you know your ovulation date if you don't then they can be useful in trying to find out approximately how far along you are. In the first trimester, any scan you have if you choose to have any, if you know when you ovulated, should look at the heart beat, formation of limbs and other body parts.

 

[Emx]

It depends on ovulation date, time it took for egg to be fertilised and implanted... lots of factors... At the end of the day from your 12 week dating scan onwards, any information regarding your pregnancy will state your EDD by LMP and your EDD by Scan! Although its also quite common for them not to bother changing the date from LMP to scan date if its only a matter of a day or two!