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Childbirth/ultrasound accuracy for conception and due dates

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Expert: - 9/24/2009


Question
Hi, I had a light period on June 13-16/17 and then took a pregnancy test on July 13th saying I was pregnant. When I went to the dr on 7/28 I was told that my due date was 3/23/2010 then on the following week on 8/4 they changed my due date to 3/24.The dr said they were using 6/17/09 as my effective last menstrual period because it looks I ovulate late. My question is how accurate is this and would my conception dates then fall between June 24 -July 2 as the online conception calculator says? I want to know because I went away for vacation on June 10-17 and although I did not have sex I am thinking my ex is going to question praternity. Thanks

Answer
Karen,


The accuracy depends upon how the due date was calculated - using the first day of your last menstrual period isn't accurate unless you have 28 day cycles and ovulate on day 14.


But, if you had an early ultrasound, which it sounds like you did because late ovulation is suspected, then the dates are accurate within +/- 3 days, meaning you definitely didn't conceive while on vacation.


I'm actually due the same day as you, meaning we most likely both conceived around June 30th-July 2nd.



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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