Conception Confusion!

Hello,
I recently had my NT scan and going by my blood progesterone results, ov pains & opk+ I guessed that I ov'd on 20th/21st March putting me at 11w6d when I went for my scan. My LMP was on 28th Feb and my midwife put me down with an EDD of 5th Dec not 10th like I believed. However, my scan dates tallied with my LMP and dated me at 12w5d! I really don't understand how the scan could point to an earlier ov day when the day 21 prog test (sent to my GP & gynae - I was on Clomid) came back as negative for ov, then a day 28 prog test came back as borderline as to whether or not I'd ov'd. Is this baby just measuring big?! I hope it doesn't mess up my sway details, that I will be posting later tonight. My GP couldn't answer this question and neither could the ultrasound tech. I measured a week behind with both ds's so it is rather puzzling! Any thoughts would be much appreciated. :)

Wow.

My understanding is that early scans really CAN'T be wrong (first to mid second tri) because babies develop at a particular rate and that really just doesn't vary by much. It's not like in the later parts of pregnancy where there are big babies and small babies and everything in between - in the early stages it's like heartbeat, check; eye growth, check; fingers/toes, check and the rate those things develop is pretty consistent by the day and does not really vary between individuals much - for sure not by nearly a week.

The blood tests I have seen come back wrong on many occasions. The first lady I ever did a sway plan for was told that she hadn't ovulated, she wasn't going to ovulate, and her hormones were just awful/infertile and she needed to book an appointment for IVF immediately (and this was from NYU and not some random crappy dr's office either) - BFP!!

Can you recall thinking back any other time you DTD in there??

i think the theory goes that early scans cannot be wrong but in my experience they can be out.

Ds1 and Ds2 i had early scans and they moved my dates by a nearly week (all my boys have measured a good 5 days out) at early scans and dating scans (i had early bleeding and scans with both). Both were late, ds1 appeared really overcooked

With ds3 when i was tracking ovulation i knew when i'd ovulated to within a day, opk's and everything else confirmed this. They were adamant my dates were wrong from my scans and moved me by a week (so i was due a week earlier), it would have mean't i'd ovulated whilst still on my period and at a time when we had not dtd for 2 weeks - not possible, we didn't dtd til just before positive opk that cycle! He was a week late and i measured big for my dates all the way through the end of my pregnancy.

This one i had a us at 7+3 weeks, they said my dates were wrong and she measured 6+5 weeks - again i was certain of my dates, i was on clomid and tracking ovulation. My 12 + 1 week scan they said was spot on (my private cvs scan), my nhs scan the week later i was 13+0, they said i was 13+4 but didn't redate me, every since then they have said she was measuring 1-2 weeks smaller than my dates (so more towards the first scan and possibly that i conceived slightly later than that - again not possible, after all the FR my poor hubby was so tired we didn't dtd again after positive opk for a good while).

Only my experience but even with the same baby and early scans weeks apart they don't seem to agree!

On the other hand you are talking mm at this stage and its mostly the measurements that actually date the baby (although they do develop at roughly the same rate, there is a scale for measurements of that date - i.e not all babies at x weeks are x.xmm precisely), measurements vary according to the human factor (all techs measure slightly differently, and baby position varies - my little girls tummy has had different measurements throughout a scan by the same tech still she got something she settled on due to babes position) and the quality of the equipment.

Thank you so much for sharing your experiences Mrs P. Perhaps its the machines that the NHS use? I am worried that they'll use it against me as I want to try for a Vba2c and if I go late by their dates then I don't believe it'll be right. My tech did have a lot of trouble getting this one in the right position for the measurements, but the first one that she did came up as 12w5d not 11w6d like I thought it should be. I still don't believe that it can be right and will be questioning it all the way. I'll be seeing my consultant in 3 weeks and will ask then.

Atomic, that's exactly what I thought too and looking back over my diary I noted that we dtd on cd12,14,16,19 & 20. I tested every four hours with ICs from 8am-8pm with no peeing in between testing from cd8-19 and the only day I had an opk+ was on cd19 confirmed with a digi. I had a fade-in on the ICs from cd17, although it was faint on cd9+10 then cd13+14, not positive though. It is entirely possible that I ov'd earlier without knowing but surely the opks, bad cramps & prog tests couldn't have all been wrong? My cm was useless that month as I had a tiny bit of EWCM on cd14, 16, 18 & 20. The rest of the time it was watery or creamy. Not my usual pattern of cm but then I was on Clomid so to be expected really.

I had a prog test on cd21 that came back 6.6 and again on cd28 that was 10.6. I pushed for that one as I knew I hadn't ovulated. I took Clomid cd2-6 that month. My GP rang to let me know that it appeared that I hadn't ovulated that month but by the extreme cramps that I felt all day on cd20 I really believed that I had ovulated then. My gynae wrote to me to inform me that from my blood results on cd21 they'd be upping my Clomid dosage.

What I don't get is how I didn't get a BFP until cd30 and it was very very faint. I know about late implantation, but I had tiny spots of blood on cd26 & 29 which would put me at about 6-9dpo from my ov dates. I did get a stronger line on my pg test at 14dpo (by my calculations) but not as strong as the control line. Both of my ds's were clear bfps at 14dpo, if my scan's right my bfp wouldn't have been until 20dpo. As soon as I got to 14dpo (by my dates) my bad PMS-like symptoms eased and the cramping calmed right down.

I'm so confused now, especially after looking back over my diary! I really hope that I didn't totally mess my sway up with dtd so often. I was happy to think that I ov'd on cd20 and only dtd on cd19, 20 and cd16 which wouldn't have counted as after a year+ of Shettles I KNOW that dh's swimmers do NOT live that long!! Really only cd19&20 would've counted if I DID in fact ovulate when I believe I did. I keep swaying between thinking that of course it'll be a boy, how could I make anything different to remembering just how different I was then and certainly it must've had some effect. I was in such poor health (sorry AS :() and with the Clomid I was a different person. In fact it's funny how the effect is still lingering a little and I'm not the bullish go-getter so much anymore. I feel a lot more meek and mild. I keep thinking about my next sway if I get a chance when I should be enjoying this pg. Silly me!

This may sound like a stupid question but could it be as simple as they (doc/ultrasound tech) are going by a 28 day cycle to calculate dates??? I only suggest this as originally my EDD was 13th Nov but in fact I only have a 23 day cycle (OV cd9). By my calculations EDD is the 8th and this was confirmed by a 7 week ultrasound. Obviously your cycle is not the standard 28 days if you ovulated on CD20 than that would put normal calculation of dates ahead by 6 days. Only a thought I may be wrong :)

Oh and I would say your chances are pretty high for a girl just taking clomid alone is a good sway

Bump for anymore thoughts? :)

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I do believe that the MOST accurate dating scans are very early. Like from 6-8 weeks. After 10 weeks, I do believe that individual development starts to take hold and measurements can be quite off from that point forward.

I know 100% when my second one was concieved (there was only one option!) and yet he measured a good week ahead at 12 weeks. And bizarrely enough, there were only two potential days for conception on my third (they were two days apart, my ov tests were super-weird), but if I concieved on the second of the two days, I would have gotten a blatantly positive pregnancy test at 7DPO (not really possible). So I assume I HAD to have concieved at the first possible date...but she always measured a day smaller than the later possible date, all the way til past 20 weeks.

I do not think I would panic about the scan. With all the signs and tests, I am sure you ovulated when you thought you did and baby is just a bit big at this stage. Doesn't mean she will stay big, just means she hit a growth spurt or the position for measurement wasn't ideal. But those scans can absolutely be off.

IMO the dates are only as sound as the tech is skilled. During my last ultrasound, I watched the tech (at a frantic pace, I might add) take the crown rump measurement 3 times and came up with 3 different dates. And I think they take an average of those 3 measurements.

Just an update on this thread. My ds3 arrived on his due date from the scan - 5th Dec! I was happy to be wrong as I got my VBA2C without any of the hassle of going overdue. :)

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thank u for updating and huge congrats! well done with vbac If you have posted pics, link me! would love to oo and aah over him! :heart: