How can my dates be wrong when I tracked ovulation ?

[Damsons]

So I went for another early scan yesterday. And measured 8+5 instead of 9+3 (5 days behind)

The 8+5 date lines in with what the other early scan said, exactly two weeks earlier I went for a scan which again put me the same 5 days behind.

what I can’t understand is if I go for my nhs dating scan and they put me behind do they take my dates into account ? I tracked ovulation and got a faint positive test 9dpo. The new date would mean I got my positive test 4dpo which I imagine isn’t possible ?

my last pregnancy my little one was tiny and born on the 0.4th percentile, I had growth scans throughout and they got her out at 37 weeks. Do they take this into consideration? I know my dates are right so I don’t want them to push me back by 5 days !

The scans get more and more accurate as your fetus grows so you may find the dates catch up. If two weeks ago the scan said 6+5 then you have the reassurance that it's growing at the right rate so hopefully that means all is okay

Thanks I guess that is reassuring !

if at my dating scan I’m still 5 days behind what I think will they take this date as due date ? Or do they consider factors of my last pregnancy and the day I got a positive test ?

Hi , try not to stress Mama when I was measured at my dating scan that was the date that stuck even though it was wrong they said they don’t change the date unless 2 weeks or more out ( but this is Belfast) could be different however private scans had my dates bang on

With my first they dated him 6 days ahead of my dates that I calculated from ovulation and they didn’t take my dates into account. Im pregnant again and they’ve dated me 2 days ahead this time. I wouldn’t worry about it, 5 days isn’t a lot seeing as you’re pregnant for 9 months.

I went for my NHS scan on Tuesday. Although they always ask for cycle length they ALWAYS base the due date from lmp based on an average 28 day cycle. I ovulate about a week later than 'normal'. So theyhadme at 12+4, but when I went for the scan I was measuring 11 weeks exactly (i expected to be 11+3, though i wasnt tracking ovulation). I was literally days away from them being able to take the measurements they needed for the NT testing (CRL hadto be over 45, I was 42.7). I have to go back in 2 weeks, but they said they would NOT change my due date until after the next scan.

Scans aren't perfect and obviously have margin for error. I believe inaccuracies are higher when the thing you're trying to measure is smaller, so I think that's why they didn't want to change my due date yet. I also think that's why sometimes people can measure even as much as a week behind at dating scans at 6,7,8 weeks, then find baby has 'caught up' by the time they get to 12 weeks.

In my last pregnancy I was tracking ovulation. Again because of my long cycles they sent me for my NT scan 2 weeks too early. Again I had to come back at 12 weeks and my scan agreed with my ovulation dates, literally to the day.

I was fairly certain of dates which aligned to early scans at 8 and 10 weeks. But they measured me 5 days out at my 12 week scan and said that's my new due date and they don't change it after the dating scan. They didn't take into account any other factors, so just going with that date now.

Does any of it matter providing baby grows well and reaches a healthy weight by around 37 weeks from first day of last period?

With both my successful pregnancies, I ended up dating a week ahead at my 12 week scan (i'd been having scans every two weeks up until then). As a previous poster said, the scans get more accurate as they get bigger.