how accurate is ultrsound?? - Mothering Forums

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#1 of 6 Old 06-03-2012, 07:48 AM - Thread Starter
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I had an abdominal u/s on 1/16 ,measuring me at 6wk/6days, LMP 11/26/11,GIVEN A DUE Date of 9/1/12. I'm 27 weeks/1Day. So far doctor has not changed my due date, baby is healthy and growing well. I dont recall having my period in Nov 2011 to have a conceived date around Dec 10,2011. Could my ultrsound be wrong?? Even though I cant recall my LMP, and having my first ultrsound showing an early measuremnt and embryo sac and just a blob with a small flutter on the screen is that an accurate ultrasound being done and in early stage of first trimester? I had another partner in oct that I was seeing and intercourse took place by end of Oct 29th. On Nov 5 and nov 11, 2011 I had nausea n vomit. But at same time I was dealing with heartburn that made me nausea. I got back with BF of 10yrs beginning of Nov and was with him Nov through Dec and till this date. I was waiting for period all Nov because I normally get my period end of month around 26th or beginng of the month they get heavy and end by 4,5,6th. Now Dec.2011 comes around and Finally decide to take a test to see.I WAS! Finally call doc for appt couldnt be seen until 1/16 My real concern I have been botherd with is did I get pregnant by the partner from Oct or It's my bf I been with for 10years??
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#2 of 6 Old 06-03-2012, 02:59 PM
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Ultrasound is notoriously innaccurate and gets more so as time goes on (it is something like +/- 7 days at 8-9 weeks but +/-3 weeks as you approach full term).  That said, very early ultrasound (before 8 weeks) is supposed to be extreamly accurate.  Definatley within a few days.  If I understand correctly, you are asking if a 6week6day ultrasound could be off by around 6 weeks and, as far as I know, it just couldn't be.


Here is a fetal development chart:


At six weeks the embryo is 1/2".  At 12 weeks the fetus is around 3". 


Here is another fetal development chart starting with conception rather than LMP:


So, at 6weeks6days you would be approximately 28 days past conception.  Using October 29th instead of December 10th as date of conception would add another 42 days (70 days).  That wouldn't even be shown on the chart above!  You wouldn't be looking at a blob in a sack--- you'd be looking at limbs!


This picture is 3-4 weeks from conception:


Here is 12 weeks (unsure if from LMP or conception, but the difference is HUGE):


When did you test in December?  Was it before 12/10 or was it late in the month?  Sometimes stress can cause you to ovulate late which could explain why you didn't have a period in November.  Did you have one in late October?  You said you normally get it around the 26th which would mean you were still bleeding while with the October partner making it very unlikely you concieved at that time.



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#3 of 6 Old 06-30-2012, 12:45 AM
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Yes, ultrasound is horribly inaccurate. I have so, so many stories from family and friends on the unreliability of ultrasound. I have known women who were told that their babies had passed only to request one last ultrasound "just to make sure" just before a scheduled D&C and found a perfectly alive and happy baby (whew!). My coworker had a boy early due to severe hyperemesis and the doctor said it was okay to just take baby out because he was 5 lbs. Turns out, baby was only 2 lbs and survived by what miracle, I have no idea. I'm glad everyone turned out okay, though! My SIL's second-to-last baby was born by cesarean necessitated by induced labor because the doctor said that the baby was too big - over 10 lbs - and had to come out early. She ended up being only 8 lbs and boy, was my SIL ever peeved.

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#4 of 6 Old 06-30-2012, 07:19 AM
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I really, really doubt it.


Although ultrasound is notoriously inaccurate as far as some things go (weight estimates in the third tri comes to mind), the odds of being off by 6 weeks at a 7 week ultrasound have to be, well, zero. There is a big difference between a 7 week old embryo and 13 week old fetus. HUGE. Likewise, if you were six weeks further along than originally thought, you'd be approaching your due date in a couple weeks. How are your fundal measurements? Are you measuring 38-ish, or are you measuring 32-ish?

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#5 of 6 Old 07-07-2012, 09:42 PM
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On my part, ultrasound had been accurate, terms of gender and due date. But I've heard some people are given inaccurate gender.. Is it the Ultrasound machine or the professionals reading the results?? But ultrasound before giving birth is really essential. My baby had a cord coil(3x), we have not known it until she was born.I'm still lucky that even though I have not done a Ultrasound before giving birth my baby survive!.Thanks God!! 

Living is great but being a MOM is even better

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#6 of 6 Old 07-12-2012, 10:01 AM
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I'm really surprised that they didnt do a transvaginal ultrasound that early on. DD was given a false due date. According to me (you know, me the one who had sex only one time that entire month) her EDD should have been 3/31/10. According to my first ob *who did a 10 week transvaginal us* the EDD was 4/26/10. She was born on 3/20/10 at 6 lbs, 8 oz. Not 5 weeks early. Maybe a week or so early, but no way was she 5 weeks early. The EDD he gave me had me conceiving after I'd had a positive pregnancy test.

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Adaline love.gif (3/20/10), and Charlie brokenheart.gif (1/26/12- 4/10/12) and our identical  rainbow1284.gif  twins Callie and Wendy (01/04/13)

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