Dating scan incorrect, any experiences?

[FenellaFurchester]

Sorry for the rigmarole. I’m wondering if anyone has had any similar experiences.

I’m 20 weeks today according to my EDD.

I had an early scan due to bleeding at 7 weeks according to my LMP. At this scan, the baby was measuring 6w1d which tied in with my later ovulation for that cycle.

At my dating scan, I was told I was 12w2d which was 7 days ahead of where I expected to be after my early scan.

I had a private scan so my little boy could see the baby which concurred with my own dates as well as the early scan dating.

Today I’ve had my anomaly scan, where baby is fine and seems healthy but has come out at 9th percentile. I’ve done all the workings out and if I am (as I believe) actually 19 weeks then baby would be bang on average at 45-50th percentile.

The issue is whether this impacts my care and the decisions made about it as I’m already on a ‘high risk’ pathway due to high blood pressure at the end of my previous pregnancy. I’m taking labetalol and aspirin, BP is fine on my calibrated home monitors - I do however suffer very badly with white coat syndrome which is muddying the waters.

On top of all this, my uterine artery doppler results were very high on one side and normal on the other side. High side was difficult to measure due to my anxious breathing.

Feeling pretty much in limbo and no one seems to want to explain anything properly (seems my local trust are so keen to avoid litigation that no one can provide any reassurance, just information)

Can I have it noted that my due date may be a week behind or even change it? It all seems so confusing.

It’s normal for dates to change between scans and LMP isn’t overly accurate. Trust the team looking after you, they know what they’re doing.

Thanks for the post but it’s not LMP it’s ovulation date which I’m certain of.
I’m sure they do know what they’re doing but they’re doing a very good impression of not knowing, the right hand doesn’t know what the left hand is doing, it seems. No communication with each other or with me. I’m constantly repeating myself for things that should be on my notes, no one answers questions or clarifies anything. Apparently the trust gives them a script which they’re not allowed to deviate from. I’ve resorted to seeing my GP to get some clarity.

I would think they would have allowances for baby to measure slightly behind or ahead so they must still be out of the expected range.

Do you have any follow ups?

Your GP is going to have literally no idea, at all. They almost certaintly won't even be able to see your maternity notes. They will tell you to speak to your maternity team.

Yes my EDD varied throughout my pregnancy. I was measuring small then big for dates and I’d also fallen pg straight after a miscarriage with no proper period after so that also added to the dating issues.

At the end of the day a weeks difference in due dates isn’t going to make a difference when baby is cooked and ready to come out. The professionals looking after you will factor any EDD and measuring discrepancies into your care if needed.

EDD is not very accurate, it’s just a good estimate. I wouldn’t worry, the maternity team will know what they are doing.

I didn’t have a LMP, ovulation date or conception date to give prior to any scan. I also wildly varied on centiles throughout pregnancy.

baby was born week 38 and average weight in the end. After being told I was too big at one point and also too small earlier on

You can’t change your due date.

Mine was wrong; categorically, from a medically assessed ovulation. They go with the date on your 12 week scan.

It doesn’t matter too much. Nobody can officially change it, so you’ll just need to be mindful when you’re making decisions. They know it’s not an exact science anyway.

If baby stays on the 9th percentile; you’ll have options. It’ll only be if they drop that there will be concerns. The uterine Doppler readings are likely to be more of a concern, but nothing to do with your due date.

I’ve had two babies that were predicted to be far too big - one totally average in the end, one on the small side; and one predicted to be very small, who was average.

Hiya, I'm in the exact same position - how did everything go for you?

I am scan trained. The earlier the scan is, rhe more accurate the gestational age is.

Thanks for this - my scan just before 8 weeks was bang on my ovulation timings but my dating scan put me forward by 3 days, which makes a big difference to the percentiles.

As best I understand it, the reason they don't take into account things like when you think you ovulated is that there's a huge amount of data based on ultrasound scans, and much, much less based on things like ovulation - so they're mostly interested in how you sit within that huge amount of established data, rather than whether (objectively) you're right about when you ovulated.

(My dates also don't tally; I did IVF so I know when the embryo went in; if I went by dates then it implanted before it was transferred. ).

EDD isn’t going to be completely correct OP, I wouldn’t worry about it. What is the GP appointment for? If it’s for the EDD they have literally nothing to do with it and no say over it.

My EDD also seems wrong - I had an early scan at EPU and a scan at 10 weeks at a private hospital for an NIPT - both of which gave the exact same date, a date which made a lot of sense to me given I know my cycle very well. At 12 weeks suddenly I was pushed ahead by quite a few days - which now also means I am measuring slightly small. And actually I’ve always been pushed ahead at 12 weeks with previous babies and I feel like a lot of people are.

I actually think I’d prefer to have the EDD as too early rather than too late. A big fear of mine is going too far beyond 40 weeks that the placenta starts to degrade. If the NHS believes you’re a week further on than you are, then this is kind of one less thing to worry about? I understand that you could just be 40 weeks but the NHS thinks you’re 41 and wants to induce, if this is a concern..?