Ultrasound reliability?!?

Ok, this may get a little confusing so please bear with me....

Today I had a dating U/S and going from my dates I should be due on 3 July so that would put me at 9 weeks exactly today. However, the sonographer told me that going from the U/S that I am 6w4d putting my EDD at 20 July.

I am VEEEERY confused!! My last LMP was 26th Sept, it was a 29 day cycle which is most likely due to my PCOS. I know that PCOS can play up with ovulation etc but DH and I didn't DTD much after I O'd so I am quite sure I couldn't have fallen pg from those times.

So what on earth is the deal?!?!? Today I saw a gorgeous little baked bean with a little flickering heartbeat which was 143BPM.

So has anyone got any ideas for me?!? :lol: How reliable are U/S?!?

When did you get your positive HPT?

I would go with the later EDD but that's because i'd want as LONG as possible before having to face potential induction...lol.

Bx

I got a HPT when I would have been 3w5d according to the U/S results. I only tested on the off chance I got a BFP. I did test when AF was due but it was a BFN and I didn't test again after that.

i would be asking your doc for a further dating scan later (another 2 weeks or so) just to see how things are traveling - you might just have a small bubba as it sounds healthy with that heart rate! u.s usually have an error window of about one week at that early. with your pcos, it's very possible you o'd late - although 3 weeks would be very unusual if you got an early BFP

speak to the doc babe - and if you need reassurance, ask for another scan...

ETA - i got BFP at what would have been, by scan dates. 3w1d, so it's possible hun!

The later date.

That way you're not stressed if bub isn't here by the early one, and early U/Ss are fairly accurate; early growth is very uniform. So uniform that in some species which have been well studied at zygote/embryo stage, in early growth a scientist can tell you how many hours old the baby is! And exactly which cell will divide next, how and when!

It only takes one sperm from one... encounter to fertilise an egg, remember, and they're quite hardy little things really. So even just once or twice a week is enough to get pg.

:bump:

I'd use the later date too for all the reasons that RF said.
The earlier the scan is in pg then the more likely it is to be accurate so I'd say that it is probably right. This is because, like RF said, growth is very uniform in the early weeks.

Get another scan in a few weeks if you need reassurance hun. Congrats, that hb is great!

I'd go with the later date for the same reasons as PPs. I would not go for a further dating scan because the only reliable dating scan is the very first scan. Once that scan has determined a due date, the date should not be altered on the basis of ultrasound (it might be altered on the basis of LMP).

I have had 3 scans with this pg so far. first one they said i was BEHIND. I was 6w4d and was told it must be less than 6w cos they couldnt see anything. second one i measured EXACTLY as my own dates should have, 12w6d. Third one I measured IN FRONT by a week. I was 184d and they said i was 19w5d.

so i just go with my own date! I am pretty confident I got it right and u/s are really not all that accurate.

(also with dd2 i was told she would be 10lb PLUS and she came out the next day at 8lb14.)

I think so much depends on the skill of the sonographer, to be honest. I've had scans that have told me I didn't conceive until *after* had a positive HPT.

And let's face it, if the medical profession weren't so obsessed with making forty days on the dot the only acceptable time limit for a pregnancy and being induction/caesarean happy, we wouldn't worry so much about dates being out a week or two!

I think I will discuss it with my GP when I see him this week.

I guess I was a little shocked that they told me I was 2.5 weeks behind what my dates are telling me but I am fine with it. I guess I just want to "know for sure". I'll see what my GP says and if he says that he agrees then the dates are fine with me. Ahhh... the joys of PCOS and the unknown!

If I were told what you were I would be thinking that I was further along - due sooner. But I had only about 5 days between the dates I was given and was told by a GP and OB and m/W on separate occasions that the earlier scan is usually the more acurate for dates.
...in my case they have just gone with the average of my cycles and given me the later date to help give me more time to achieve a vbac.

Congrates on your pregnancy.

:

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DH and I didn't DTD much after I O'd so I am quite sure I couldn't have fallen pg from those times.

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Only takes once though, perhaps in one of those few times you actually did fall preg.....
As people have said u/s is only as good as the sonographer. Dates can easily be out by a week either way. I knew the exact time of conception for this preg as we only DTD once! :redface: My scan was a week different to the date of conception. So there is clearly a little variation. But i wouldn't expect 2.5 weeks difference. Maybe it is just somewhere in the middle. ;)

Nice to have a few extra weeks up your sleeve though. :D

im gonna jump in real early & say your having a boy.