Had first scan today

[MrsHormonal2019]

Had my first scan and all is good. But they've put me a while week ahead of where I was going by lmp.
According to my fertility app I got pregnant a week before I ovulated. Literally days within period ending.
It just made me think that if people are only having sex around when an app says they ovulate, which I've read people do, they must be really knocking their chances.
Anyone else conceived on a completely different week to what lmp or estimated ovulation on a typical cycle said?

I think it depends what your cycle is like. Mine is bang on 28 days so I knew my fertile days without needing an app. But if your cycle isn't as regular, it's probably wise to have regular sex to enhance your chances.

My due date was a week earlier when I went to have my scan, I've heard the dates are often changed at this stage and the due date is stuck then and doesn't change again at a later date. I must have conceived right after my period too! lol

I wouldn't read too much into it, my son was from a donor egg IVF cycle so I knew to the hour when he was fertilised and transferred and the NHS put me a week ahead when they scanned me

I believe it is mainly done on size, and so your baby may be just a tiny bit bigger than some at this point. Issue is their measuring is often inaccurate due to babies position etc and a matter of millimetres can make all the difference!

Honestly, don't worry 😁

How many weeks are you OP? If it's a early scan they are not reliable dating wise. Mines an ivf baby and my 7 weeks scan measured wrong. By my 12 weeks scan I dated exactly right

Got pregnant first try using an app.

They don't actually tell you to have sex on your ovulation day as that isn't the best time. It's during that week so that when you do ovulate, there is already sperm there.

That being said it does also make a difference what app you use. Mine was using my temperature so was very accurate, just doing by cycle day isn't as accurate.

I'm a standard 28 day cycle and I was 12.6 by my lmp but they've put me at 13.5 now.
Tech told me all babies are same size at this stage and tall and short come into it further down the line.
But yea it's definitely weird.
I had coil out, had my period a few days later and then pregnant a few days later.
I thought from what I've read womb needs a week to rebuild after period and then you ovulate. Not mine apparently o_O

Oh also I've just re read your post.

The hospital/Dr tends to put you a week ahead of when you actually conceived anyway as they tend to do it from your period dates and then it doesn't change unless your scan shows something very different. They do it because most people don't know when they actually conceived.

No the scan has put me a week ahead. Lmp said I was 12 weeks but dating scan says I'm near 14. Just confused me is all.

Yes that's normal! They always do it from you period unless the scan shows something very different.

It just goes off the sizing of the baby.

I know exactly when I conceived because it's the only time we managed to DTD, but my scan date put me a week ahead.

With regards to them saying there's no bigger babies etc at this stage, that's a load of nonsense.

I had my first scan at what should be 6w, then a full week later, I measured 7w1 (a day ahead). Four weeks later, I measured 11w5 (when based on first scan, I should have been bang on 11w), then at my official 12w scan when I should have measured 12w1, I measured at 13w bang on.

The very first scan was accurate in terms of conception dates, but he had a growth spurt before his 12w scan placing him ahead, and he's continued to measure as a big baby and ahead of what he should do throughout every scan we've had.

I ovulate really regularly usually (either cycle day 13 or 14). This last cycle I ovulated on cycle day 10, luckily we'd had sex on cycle day 9 just for fun!

It's nonsense that they all measure the same size. The scanning equipment uses a specific algorithm that dates the baby based on the mean measurement for a certain gestation. I know when I ovulated this time and have done clearly in the past. Scan is dating me 9 days ahead of where I should be!!!! I had literally just started my period then.... but I also tend to have big babies and am tall (5"11).....

We can pinpoint our pregnancy not just to a date but to an hour of conception (IVF pregnancy with donor eggs) so there are no questions about our dates - however at a scan at 12+5 one twin was measuring 13 weeks and the other was measuring 12+3 - from that scan they moved my due date to 2 days later than previously by using smaller twin instead of larger one.

This just goes to show that babies do vary in growth even at that early stage in the same way that some babies are born long and skinny but others are squat and chubbier. Then I changed hospital and they agreed to use conception date as the absolute whereas the previous hospital had been using my LMP which was changing my due date even more than the scan did.

That's mad. Weird how they work it then if it's not even accurate. What's the point. So you could have women week early or more or over due because of a scan

I do think it makes more sense to date from a scan rather than LMP as people ovulate at different points in the cycle and also the window for implantation can vary between 5-6 days so even with 2 women with the same LMP the implantation date could easy be 10-12 days different

Scan dating is a particular bug bear of mine. It just doesn’t make sense as the measurement error must be huge (the difference in length of the same baby measured numerous times - I don’t believe you can accurately measure the length of a foetus on the screen in a way that means it will read the same across multiple readings and different people). My understanding is that that length reading is then extrapolated to the 50th centile to give the due date. Which would be ok, but the due date is used to decide whether and when intervention (e.g. induction) should be given. It’s wildly inaccurate and has a huge bearing on birth outcomes. It also assumes that foetal growth is linear (baby grows the same amount each day, no growth spurts). It’s madness!

Our first baby was a honeymoon baby and I hadn’t been paying attention, so the scan date was the best guess. But my second I know exactly when we dtd, and also felt implantation. They were about a week out with the date (they had me at 11w, not 12w), so my baby was born on his due date (irritatingly as I had protested that date repeatedly), but was actually a little over 41w by my calculations.

Putting your gestation further on than you think (so 13w instead of 12w) could have a knock-on effect for birth, wrt induction and is worth thinking about when you come to make those decisions.

Having a similar issue myself at the moment. I'd been using Natural Cycles (for contraception) for nearly 3 years before we TTC so I know my body really well (I appreciate that most apps only go on period dates and work on averages but this one does BBT and and OPKs to pinpoint ovulation). I have a constant luteal phase but ovulation does vary a little. The cycle we conceived I ovulated a few days earlier than average (had just started testing with OPKs and got a blazing positive!) but the midwife refused to take my data into account and write down LMP date which was frankly a load of 💩. I then had a scan two weeks ago before the Harmony the test and the consultant measured CRL to be just one day out from my ovulation date, so far all okay - I am quite okay with that margin of error and I felt like the consultant was talking to us both on an equal footing (we both have science/maths backgrounds).

Had the 'dating' scan on Tuesday and the CRL was 5 days ahead (and one measurement was even 7 days ahead - they take several). I tried to have a discussion about accuracy with the sonographer but she rolled out the 'sperm can last several days' argument and had no answer to me when I pointed out that that would only work if you moved someone back by that amount - the dates I now have basically assume conception occured 4 days before there were any sperm anywhere near me (and that's ignoring the fact that the egg hadn't even been released by that point 🙄). The only thing she said I should do is discuss it with my midwife at my next appointment 🤷.

I feel not listened to, and frustrated that they won't take on board information which is more accurate as part of the picture. My DH looked up CRL on Wikipedia when we went for a coffee afterwards and there's a graph on there that shows the error bars at various gestations - from it, my dates are within range for the measurements, but they're above the mean value. I've also seen various other information suggesting that accuracy is highest between 8-11 weeks (I was scanned at 13 - by my dates).

It's making me think I should have lied when asked about LMP and just taken the full 14 days off when I know ovulation happened rather than being truthful.

@stillworkingitout

Cross posted with you but YES you are bang on with my concerns.

According to my due date we conceived during a week where we had no sex whatsoever

@pattyhoo 🤯

Hah! We are also both scientists so I feel my concerns about the measurement error are real and valid. But people taking and using the measurements don’t seem to have the right understanding of large data sets to understand my issues.

With our 20w scab there was a concern about some measurements so I got some obstetric papers and replotted the values and recalculated the errors to show that the measurements were ok. I’m sure my midwife thought I was insane

@stillworkingitout awesome! My DH is actually suggesting we go armed with data to the 16 week appointment to settle my mind and if the midwife won't listen (as we're expecting) then I'm planning to ask to speak to someone more senior about it.

medical professionals don’t always like being confronted with journal articles. It can lead to some interesting conversations- good luck!

Perhaps the more important thing is that you feel empowered later on in pregnancy to make your own decisions, if and when it comes to deciding about intervention. Everything is optional, even though it’s rarely presented that way