ultrasound and fetal age prediction at 20 weeks

Archived User

ultrasound and fetal age prediction at 20 weeks

Hi, I'm a big fan of your research and writing about labor and birth - you could say I'm a long-time reader, first-time poster...

I got pregnant at the beginning of January, and know within 7-10 days when I concieved. Because I am still nursing my two-year-old, and hadn't had a period to base my pregnancy off of, I agreed to an early dating ultrasound. I estimated I was around 6 weeks, 2-3 days when I had the u/s, and the actual machine dated me at 5 weeks, 5 days. The tech then went to a different computer and told me it would compute my "official" date, which was 5 weeks even. I was happy with the date (though I knew it was at least a week later than I really was), because I didn't go into labor with my son until 41 weeks 1 day, and am planning a VBAC for this birth.

I had my routine anatomy scan last week, and the tech/attending OB moved my due date from October 6 to September 22/24. I want to either keep my original due date, or only move it up a few days at most, as I want be able to go into labor on my own, and not be battling against a repeat c-section at the end of this pregnancy. I have an appointment with my midwife next week, so I don't know how hard and fast she plays by the rules regarding a changed due date, if at all, yet.

Can you point me to any research or literature about the accuracy of estimating due dates during mid-pregnancy?  Any other advice about this situation is greatly appreciated, especially in regards to what I can do as a client in keeping or advocating for my original due date. Thanks so much!

Henci Goer

RE: ultrasound and fetal age prediction at 20 weeks
(in response to Archived User)

Definitely insist on sticking with the 1st trimester ultrasound due date. First-trimester ultrasounds are more accurate: "The earlier the ultrasound assessment the more accurate the prediction of date of delivery,"   and, if that weren't enough, the date agrees with your own estimates, which is strong confirming evidence.

-- Henci

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