Confused with ultrasound

[Mumma2212]

So i had my lmp on the 4th November. I got a edd of the 12 August i tracked my cycle as we were actively trying to conceive. Had a 9 weeks scan that gave me the due date of the 15 August. Then I had my 12 week ultrasound and they put me forward to 13 weeks with a edd of the 7th August.. that cant be correct as i would have conceived on my period. Im very confused how does this work

They work out the due date on average sizes so your baby is measuring the average size for 13 weeks. That doesn't mean if you back date that's when you conceived- it's just the size of the baby. (That's my understanding anyway).

They normally go by the size of the baby so I guess yours is growing a little faster/bigger than average. The due date is not very indicative of when the baby will be born, I've been told anywhere between 3 weeks before and 2 weeks after the due date is considered "full term", so I wouldn't worry!

Mine is growing faster as well, my 'official' due date from the dating scan is five days earlier than from my dates which is pretty much impossible, but hey ho. He'll be tall like his dad!

Your due date is a bit meaningless - you can be full term anywhere between 37 and 42 weeks so take it with a pinch of salt! The date won't make any difference to your baby, as long as they are growing at the right rate and you're prepared for a late July - late August birth you will be fine

Remember pregnancy is dated from ~two weeks prior to conception, so 13 weeks means you conceived 11 weeks ago. Which would be 18th Nov. Conceiving around 4th November would give a due date end of July.

(Assuming you are 13 weeks today that is)

Yes i understand about adding 2 weeks but when i use my conception, ovulation tracker and use the edd given by hospital the 7th aug, that means i would have had my lmp 2 weeks before i actually did and that i ovulated when i had started my lmp. But when i use my dates i get the 12th aug and points the ovulation window to when we did dtd as only done it on the two days during ovulation that month so i know conception was roughly then. Just because know ultrasounds had a margin of error to so might just be a mistake ill stick with my edd and go from that

That's only a five day difference between 7th and 12th though, it's really nothing unusual for the dates to change by that much at the dating scan :) Mine did as well and I know it can't be right, but it is what it is, and at the end of the day it doesn't matter that much. Only 4% of babies are born on their due date anyway.

First of all congratulations 🎊

It does sound that your baby will be on the slightly taller than average side. I would feel more comfortable having a baby measuring bigger than average on a scan than a scan saying the baby was lagging behind in size for its conception date.

And as we all know babies have a habit of coming when they like. Both of mine were born at 36w 4d - my body does not seem to be a fan of late pregnancy!

OP I was in the same boat as you. I knew my dates due to having a regular 28 day cycle and ovulating on day 14 (confirmed by OPKs and BBT spike) and knowing when I DTD! I went for my 12 week scan at 12 weeks but was measuring 13 weeks. It just means the baby has had an early growth spurt! They're not telling you when you must have conceived. So my due date was brought forward one week compared with where the midwives (and I) had put it based on my last period.

Sure enough, I'm now full term at 40+3 and baby is showing no sign of wanting to exit - quite possibly because it knows it's actually only at 39+3!

A piece of advice - maybe tell friends and family the original due date - you'll save yourself a week of "any sign?" texts!