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Childbirth/Ultrsound accuracy
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Question
Hello
I have a question regarding ultrasound accuracy and conception. I have a history of PCOS so no LMP! Started feeling sick 3rd week in Oct, tired, sore boobs, posisitve pregancy test that week. Had adominal ultrasounds at 8 weeks that dated me to 24 Sep conception and at 12 weeks which dated me 23 Sep conception (have counted back 6 weeks and 10 weeks to take account of LMP).
How far out can ultrasounds be that early? I had a previous partner on 3 Sep and really dont want it to be from that! I took a negative pregnancy test on 26 Sep.
Thanks for your help!
Kay,
Transvaginal ultrasound between 8-10 weeks is the most accurate way to date a pregnancy, with a standard error of measure of +/- 3 days at most. So, if your first ultrasound dated you to 8 weeks, you would count back 6 weeks for your conception date. For the second ultrasound, you would count back 10 weeks for your conception date. From your question, it seems that you counted back 6 and 10 weeks for your LMP, which wouldn't be correct - counting back that amount yields the conception date since weeks of pregnancy are calculated from the LMP date.
Best,
Catherine
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Answers by Expert:
Catherine Beier MS CBE
Expertise
I can provide evidence-based information and current research findings concerning childbirth and pregnancy. My specializations include natural childbirth, pregnancy and birth interventions, fetal positioning, labor induction, choosing a care provider, midwives, homebirth, unassisted birth, natural pain relief, medications in pregnancy and birth, informed consent, understanding the risks and benefits of childbirth choices, doulas, waterbirth, childbirth methods, childbirth education classes, cesarean section, and VBAC.
Experience
I have been a childbirth educator, mother, author, public speaker, researcher, and birth advocate for the past 9 years. I am also the author of Giving Birth Naturally, a site dedicated to natural childbirth and pregnancy information. I publish evidence-based articles on pregnancy, childbirth, newborn care, and post-partum care. I'm also a mother of three children, two daughters and one son all born naturally. To learn more about what normal birth looks like, view the natural childbirth video of my son being born at home unassisted.
Publications
My book, Birth Outside the Box, was published in 2007.
Education/Credentials
I hold a Master's degree in communication disorders with an emphasis in child development. I am also an independent childbirth educator.
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