Ultrasound accuracy?

[MsKitty84]

How common it is for early ultrasounds to be off in the first trimester, and how much? Doc wants to do one more checkup. My dates don't work so we've spent the last couple weeks trying to determine how far along I am. If I go by last bleed as LMP, I should be 7 and 2, but yesterday's ultrasound showed the sac measuring 5 and 4, and just a hint of fetal pole. No clear pole or hb yet. (Another post explains the whole story.) It was still a huge change from my first ultrasound, where we just saw a thickened lining and a small dark spot.

If the ultrasound dating/measurement is right, that puts me with a positive urine pregnancy test (!!!!!) and a blood HcG level of 660.6 (overheard the nurse) at just 3 weeks 4 days, since those results were from my first visit. And it means I would have been maybe 2 weeks, 3-4 days pregnant when I called the clinic to make my appt.  Is it possible?? Even an early result home test isn't supposed to work that early!

[Ashelen]

Well if you're at about 700 now (let's just round up since they should be increasing even as we type ;-) ) and you can expect them to double approximately every 48hrs...within a week you should have a high enough concentration that you could expect to see something more developed.

Realistically the range for "expected" hcg during any time of development is HUGE..I've known women to miss their period have be well into the 2000's the same day, and some women who only have 200-500 that same day...and have gone on to have normal pregnancies. So as far as what you would expect at this stage I wouldn't focus on that, I would just focus on when you can expect the numbers to be high enough to see a fully developed pole...and from what I've learned, it would have to be at least 2500+.

[MsKitty84]

He said normally he'd wait two weeks but he's equally confused and wants to know what's going on lol so back in in a week.

[MsKitty84]

Would it be normal to expect blood HcG that high so soon? Everything I can find says that level's normally found more like 4-5 weeks.

[Ashelen]

sorry meant to say that the 5w4d was probably accurate, not the 7w2d^^^

[Ashelen]

Well...first trimester ultrasounds are almost always very very accurate. I'm just as baffled as you are, having followed your story from the beginning, but either way I'm very glad that there seems to be a little beanpole in the sac and I'm hoping the next ultrasound can give you a more definitive date. I do know that once they find a heartbeat and can measure the actual fetal pole they'll have a more accurate measurement...because sac sizes themselves can vary so much that it's hard to get a totally accurate date off of that alone.

When is your next ultrasound? usually hcg levels have to be above (opinion seems to vary on this) at the LEAST 2500-5000miu before you can see the heartbeat and a fully developed fetal pole...so I would say in the next week or two you should be able to get a clearer picture and a more thorough measurement. I'm not a doc, just going by experience, but that would be my guess :-). the 7w2d is probably fairly accurate (maybe a miscarriage followed by an immediate conception, like you've thought before?) but they'll zero in on it more with the next u/s.

[SiSi_]

I got a positive home test at 3w! Very possible :)