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Expert: - 12/18/2008


Question
Hi I am very sorry I got my first scan on the 7th Oct which said I was 6 weeks 2 days then recieved second scan on 17th Nov which said the baby was slightly bigger at 13 weeks, but my due date would be the same.

I have irregular periods and wanted to know if this would mix up my dates. Can my scan have been 3-4 weeks out and I could have concieved on the 10th Aug this would have made me 10 weeks on my first scan and 16 weeks on my second instead of 6 and 13??

Thanks for your help.

Answer
Kerry,


There is no way you conceived on Aug. 10th given your information.  Early ultrasound, typically between 8-10 weeks gestation, is the most accurate predictor of fetal age since babies grow at much the same rate during the beginning of pregnancy because genetic factors and maternal health/diet don't play a role at this stage.


The typical error of measure at your first ultrasound would have been between +/-3 days but not weeks off.


So, given the information you gave previously, you still most likely conceived in the beginning of Sept, not Aug.



Best,
Catherine

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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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