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Ultrasounds measure the size of the fetus to predict a due date and are usually very accurate, within two weeks, so I would safely assume that it would not be off by five weeks. You can ask your doctor, it won't be the first time he or she has answered that question,I promise.

Also it depends on when the U/S is. U/S before 12 weeks of pregnancy are very accurate, plus or minus 2 weeks. After that there are more varibles, babies grow at different rates so they are not as accurate.

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โˆ™ 2015-07-15 21:38:21
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Q: How accurately can an ultrasound determine the date of conception?
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If a woman's periods are not regular and she falls pregnant how accurately can one then determine the conception date from an ultrasound?

For about the first 10-12 weeks all babies grow at about the same rate so term date can be calculated fairly accurately, you then count back 38 weeks for the date of conception. After 12 weeks babies may not all grow at the same rate so it becomes less accurate.

If you are 11 weeks pregnant how do you determine the conception date?

Conception date is based on your last ovulation cycle prior to when you didn't get your period. But this can be incorrect if you didn't conceive when you was ovulating. Alternatively you can have a ultrasound scan which will give you a conception date but this can be off by 5 days.

Which is the date of conception on an ultrasound?

Ultra sound scanning does not give the date of conception, but examining the picture produced an estimate can be made.

If you found out your pregnant on April 24your lmp started on March 23 when did you get pregnant?

An ultrasound will determine the date of conception by measuring the fetus. You conceived somewhere between March 23 and April 24. It is difficult to pinpoint the exact date of conception this way without an ultrasound to measure the fetus.

When was conception date if due date by ultrasound is 1 of Sept?

November 24, 2011

Are the conception dates from ultrasound different with twins?

No. They are conceived on the same date.

Can one determine the date of conseption closer that two weeks?

I am guessing you mean that you want to know your date of conception? It really depends on a couple of factors. If your normal periods are regular, you can be fairly accurate with conception date within a couple of days. Count back 14 days from when your period was DUE (ie but didn't come because you were pregnant) and this will be around the time of conception. Conception date will be within two days either side of this date. If you are pregnant now, an ultrasound will tell you very accurately what your conception date is. As long as you have an ultrasound within the first 10 weeks - the earlier the better. An experienced ultrasonic person can tell you down to the day - ie six weeks and three days.

If an ultrasound estimates your due date as September 24 what are the chances the conception was on January 13?

It doesn't look that likely. I'm due September 26th and my estimated conception date was January 5th. If the ultrasound is done in early pregnancy (First Trimester) the accuracy of determining a conception date is within 5 days before or after the conception date, so you have a ten day window. Hope this helps!

When an ultrasound gives me an estimated due date do i count back forty weeks to get an estimated conception date?

No, you count back 38 weeks for the conception date, but don't forget this is just an estimate.

Would excessive drinking the first trimester alter the measurements of ultrasound to determine size and conception date And if so how many days off could it be?

NO ultrasounds measure amniotic fluid and the fetus head, this would not alter you're conception date. If you wanna know you're conception date go to and they will calculate the time you conceived based on you're due date. It's just an estimate. GOd bless

How can you determine your conception date if you still have a period?

you are not pregant if u still have it

If during a ultrasound the doctor says the baby is 16 weeks along does that mean 16 weeks from conception or Last Menstrual Cycle?

It means from the date of conception.

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