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Baby measuring 11 days ahead at 20 week sonogram
Help! According to my LMP of May 20 I am due February 24.

I had an ultrasound done at exactly 9 weeks and the baby measured in at 9 weeks 6 days. The Dr. did not change my due date based on this scan though.

Yesterday I had a sonogram at 20weeks 6 days (from LMP) and the measurements estimated the baby was 22 weeks 3 days! And my due date might be moved to February 13! I guess I was expecting the baby to measure a few days larger, but not 11 days!

Based on the latest measurement I would have conceived while I was on my period and I didn't have sex until May 30 so there is no chance that happened. The person doing the sonogram was acting like he didn't believe my LMP date of May 20, but I'm 110% sure it was a period. My period before that was April 23.

Is there any way I possibly conceived after the April 23 period and am just now realizing it? Could I just have a big baby?
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1026926 tn?1292117415
No you probly did not. Ultrasounds done after the first trimester are less accurate. They may be up to 2 weeks off.....give or take the two wks. Most physicians know this and will not change your due date unless the difference is greater than two weeks. This happened to me with my last baby and I convinced the doc against his wishes to change my due date so the date would be almost two weeks sooner. When my son was born we discovered he was 5 wks early since I went to the hospital with mild contractions and they went ahead and induced labor because they thought I was close to my due date. You want your baby in there as long as they are supposed to be. I would keep your original due date.
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1039620 tn?1272597604
Later scans are not as accurate as earlier ones. They can easily be off by a couple weeks since after a certain point babies grow at different rates. I believe that after the first trimester they can be off by quite a bit, compared to only a few days if done early. My OB said they never use scans past 16 weeks for dating because of that. I would try not to worry about it too much and stick with your original date.
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1039620 tn?1272597604
Seems like sprarah and I were typing at the same time. :)
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Sounds like you've just got a chunky baby. Earliest sonograms are the most accurate. Good luck and congrats!
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726324 tn?1324078210
How long are ur cycles? The due date based on ur LMP is not that accurate, they are probably basing it on a 28 day cycle. They should take it from ur conception date if u know it i.e. when u ovulated. If u had sex on May 20th and not again after that chances are you conceived around this date. As people have already mentioned. First trimester scans aren't always that accurate. Good luck x
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u  are probably just going to have a big baby i had my daughter 4 weeks early but my ultrasound the day befor i had her measured her a full term baby but there was no way that she was because of the dates i conceived she was 36 week fetus but measured 40 weeks she weighed 7 pounds 11 ounces at birth dont be nervous if u end up having the baby early hope this helped
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Thanks ladies!

kerriekab- my cycles are 26/27 days long. LMP was May 20 and we had sex on May 30 which by my calculations would have been the "winning" sperm, LOL, so maybe I ovulated just a tad bit early or just have a big baby.

Thanks for all the advice! Long term "lurker", first time poster!
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1026926 tn?1292117415
Just wanted to add with my first son the first ultrasound in the first trimester was right on with my LMP. They did an ultrasound in my third trimester and told me I may have to have a c-section because with their measurements he was going to weigh over 10 pounds and they did not think I could have him vaginally. He was born 7 days before my due date and was only 7 lbs 4oz......so yea later ultrasounds are not accurate lol
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