Is the pregnancy scan completely right?

[NewMummy2be]

I had my 12 week scan a month ago. Which put me perfectly on track at beggining of my LMP which was beggining of April. However my last period was very light beg of April. We only had sex at the end of Febuary And again middle of April. there is a two week gap between when we had sex. Could the baby of been concieved end of Febuary even tho the scan is dating it for April? How accurate is the scan?

I think dating scans tend to be pretty accurate as they get your due date by measuring the baby. 2 weeks out, that early in pregnancy, is a fair bit of growth difference.

Thats what i thought. I just cant understand why my period was so light. It was only 2 days. So now i feel further on. Yet the scan said from LMP.

My 12 week scan was way out. They re-dated the pregnancy at the 20 week scan. Nobody listened to me at the 12 week one though, despite me being absolutely sure of my dates and having had a private scan early in the pregnancy which showed a heartbeat that wouldn't have been there with the NHS estimated dates.

I just had to live with it for a while until they reassessed and changed their minds.

So you're saying either your 12 week scan is right (conceived mid-April) or out by 6 weeks (conceived end of February)? Scans CAN be out but not by 6 weeks. It's much more likely that you just had a light period in April and then went on to conceive.

I did ivf, so I know EXACTLY when 'conception' happened - at my 12 week scan they said my EDD was wrong and brought it forward by 4 days due to baby's measurements

So no it's not exact, but 4 days is a bit different to 4 weeks

LMP is such a pile of poo. Having been trying for ages and had a few mcs I knew my cycle like the back of my hand so was able to explain when i went in that i WASN'T x weeks i was y weeks. I know i'd be measuring a whole week behind if i stuck to my LMP. The dating scans seemed pretty accurate but i'm guessing it all depends person to person :)

Scarlett the same happened to me. I had IVF and they told me at 8 and 12 week scan I was three days later than I am. Erm think i know when the blastocyst was put back

I know exactly when I conceived as I was being looked after by the fertility clinic. Scan put my date as being 4 days earlier than what I calculated which could not have been possible.

But I think unlikely that they would be two weeks out.

My 12 week scan was 10 days out. I knew it was.
We used to joke that I got pregnant while my husband was away!

Cherry, wouldn't that be because a blastocyst is already a few days old though?

they told me at 8 and 12 week scan I was three days later than I am. Erm think i know when the blastocyst was put back

That doesn't make it "wrong" though. Pregnancies can vary quite widely in how long they take to implant even for people who had sex (or IVF, or whatever) on the same date. And the point of a dating scan isn't to figure out when exactly you conceived, it's to figure out when you will most likely give birth based on the size and development of the foetus. There isn't really any point in looking back and calling it "wrong".

OP I really doubt your scan is 6 weeks out. The difference between the visible foetal development of a 12 weeker and an 18 weeker is significant. It's not just a question of size but anatomy. You probably just had a light period in April.

ijustwantodance the fertility nurses and consultants go through it all (cant remember all exactly) and show you how it works and tell you the exact date. They put a couple of days in to account already of the blastocyst.

Based on my new due date, the embryo implanted while it was still in the lab