How accurate are 6 week Ultrasounds?

I had the vaginalt Ultrasound because my periods are like 2-4 months apart and didn't know how far I was, it said I was 6 weeks 2 days. I had another one (partial ultrasound) at 14 weeks and she said it was right on with the first one. Now my doctor is saying my uterus is measuring a week ahead of what the Ultrasound is saying... so I don't really know which one to rely on for my due date?

4 Answers

  • 1 decade ago
    Favorite Answer

    In general, ultrasound dating of a pregnancy is more accurate than dating using the date of the mother's last menstrual period. The biometric crown-rump measurement (CRL) of the six to 12-week fetus provides the MOST accurate measurement - within three days of true gestational age. From 12 to 18 weeks gestation, other anatomic structures are typically measured and biometric measurements are usually accurate to within a week of gestational age. After 26 weeks gestation, fetal variability has greatly increased and the dating provided by biometric measurement is less accurate, but the method is still used. By late in the third trimester, measurements are accurate only within a two-to three-week window.

    Source(s): Due 10/21
  • 1 decade ago

    the ultrasound at 6 weeks is the most accurate. It is when your baby is still a bean and is easy to measure. The farther along your pregnancy is; the harder it is to tell how far you are. All babies grow at diffrent paste, and yours might be growing a week ahead. Listen to the first ultrasound.

    Source(s): Have me for Sep 22 which I concieved December 20-24 (5 STARS) By my LMP they have me for Sep 14 I am sure when I got pregnant, plus my ob/gyn told me that, lol
  • 1 decade ago

    The ultrasound is right...with my first i measured a lot bigger and i had a ultrasound done to make sure there wasnt twins...but it could be a big baby...oh i just had one baby in there should be right

  • the ultrasound is the most accurate.

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