Can dating scans be wrong?

[TotorosOcarina]

I had my dating scan a while ago and am still really confused.

I'm plannng my 3rd homebirth (4th birth) and my dates just do not add up and I'm worried about being seen as 'overdue' by the scan dates and not being allowed to deliver at home.

I wa going to be 13 weeks that day by LMP.

But by my calculations - the fact I OV day 21 and the date I got my BFP (after testing daily) I put myself at about 12+1

however scan said 10+4

even the midwife said it didn't make sense as by that dates I got my BFP at the time of conception!!

Sonographer said 'you are def 10+4'

andyflo - I am a scientist, so I am very much for well-researched evidence-based medicine. But there are lots of cases on this thread of women who had fertility treatment and were given dating scans that were wrong. Including me. I could tell you to the minute when my DDs were conceived. :) How do you explain that?

another one here - not fertility treatment but my scans at 9 weeks and 12 weeks put me a week back so that conception would have been a week before I ov'ed. Before everyone says you never know exactly, I was charting from every possible angle, plus we didn't have sex until several days after the scans say I concieved. I know to within a day or two - the midwife agreed with me incase induction becomes an issue.

I think the point is that we all agree that scans can be off by up to a week or so, I don't think anyone disputed that.
However, in the case of the op, the sonographer who posted here has confirmed there is a huge difference in how the baby LOOKS at the two stages in question. Surely that is the main point here.
From my own experience, a scan at 9w showed a blobby thing with 4 stumpy limbs. An 11w scan showed a definite obvious baby.

I thought that the point was that dating scans are often used as the reason for induction, because the woman is "overdue". Except that she knows that she isn't. The woman is then likely coerced into having intervention that will increase the chances of intrumental delivery or C section. And all for no real purpose as she isn't actually overdue.

A week is a long time when you're "officially" 41+6.

I must go back and re-check my scan dates, as I'm sure the difference was more than a week, even in the first trimester.

I'm sure my scan was wrong. By my calculations, DD should have been born round about the 7th of June. My dating scan brought it forward to the 31st May. However, DD was born on 12 June and weighed 7lbs, so not exactly over-cooked.

My scan with dd2 was initially dated at 10+4 by size but the somographer was in training and being supervised and the scan was repeated because it was v different from my dates. Repeated and 12+1. Spot on. Even if scans are rarely wrong by more than a few days, are scanners really saying there is no place for human error?

Yesss...Mollycuddles, there is a place for human error as is the case of your trainee Sonographer...Sadly Ultrasound is largely unregulated and any Obs/Gyn can scan with little training (despite Sonographers training 3 years degree then 1-3 years post grad masters)not to mention the private sector where basically anyone can buy a machine and set up!!
The official line (checked my stats with collegues today!) is up to a 5 day margin of error, however, with the advent of NT and CRL having to be soooo spot on for accurate screening I argue that it is a day or so...
Thankyou to vmcd28 for really READING my post and the important note that babies of differet gestations LOOK different!!!! I sometimes feel that some posters on here want to jump on a bit of a band-wagon and shoot down professionals who just want to help!!!
Yes, totally get the argument for women who Know when they conceived etc but for every one of them there is a Jeremy Kyle wannabe, trying to 'make their dates fit'...so unfortunately a standard line has to be taken nationwide. Xx

I am really confused yesterday I went to a scan for testing only to findout that the scan gave me 16 weeks full while i am not 16 weeks pregnant but I am 13 weeks pregnant I don't know why it's giving me more 3 weeks forward

@totorosOcarina the dates you've given do add up.
If you are testing daily, and your first positive was on the 24th August, let's assume you got that positive at 10dpo. That means you ovulated on 14th August.
14th Aug - 14th Oct = 8+5 weeks. Add on 2 for dating = 10+5.
10+4 is absolutely realistic.

Bahahaha zombie thread! Didn't look to see it was Oct 2010 and not 2021 🤣 assumed it all worked out for OP in the end 😂