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Yes, don't worry about the difference.

By 4 weeks, a fetus cannot be seen but the thickening of the uterine lining can be detected. By around 5 weeks, an ultrasound can almost always confirm that you are pregnant.

Between four and a half to five weeks, the gestational sac is easily seen and can be measured, since the average growth is 1mm per day at this time but not completely uniform this information is considered a tentative date when LMP date is not known.

A few weeks later Ultra Sound to determine fetal age is done by taking a measurement of either the femur (longest bone in the body) or the crown of the head to the pelvis called the "crown rump". The measurement is taken and automatically then by comparing your baby's measurements to the data from a large collection of measurements, the ultrasound can then tell how far along your baby is.This is most accurate between week 7 and week 14.

Doctors have fallen into using a rule in ultrasound that when the due date based on ultrasound doesn't vary from the mother's dates by more than a week, stick with the mother's dates; if the ultrasound disagrees by more than a week to ten days, it becomes wiser to rely on the ultrasound.

Later in pregnancy other things such as babies who are larger than average size, babies growing at different rates among pregnancies, will cause inaccurate dating of pregnancy. But are still an excellent tool for other issues that may develop.

The bottom line is, Ultra Sound is a machine made and run by humans, it is an amazing tool for many things, but babies are still going to come into this world when they are ready, regardless of dates. Only 5 to 10 percent of babies arrive on their due date, whether the date is by ultra sound or LMP.

2015-07-15 20:51:55
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Related Questions

How accurate are ultrasounds in determining when you conceived?

At 7 weeks an ultrasound is accurate within 2 or 3 days. At 20 weeks it is accurate within 5-7 days.


How soon can a ultrasound tell if your pregnant?

You can tell you are pregnant through ultrasound as early as 4 weeks with a vaginal ultrasound.


Can an ultrasound be off by a month in the first trimester How accurate is an ultrasound at 7 weeks?

Well I had an ultrasound at 13 weeks and it was not very accurate. and it will not be able to tell the sex of your baby. Oh by the way, depending on what kind of insurance you have and what hospital you are at you may not get another ultrasound. An ultrasound at 7 weeks is extremely accurate, within 2-3 days. At 13 weeks it will be accurate within about 5 days. It can certainly not be off by a month.


The ultrasound said that you were 12 weeks and 1 day pregnant how accurate is that?

as accurate as you can get. they told me with my 3rd baby that I was further along then we thought,and she was born the day they predicted.


How off can an ultrasound be that estimated your last menstrual period the same at eight weeks and twelve weeks?

I think this is what you mean. For example. On 28th December the ultrasound said you were 8 weeks pregnant, then on 25th January it said you were 12 weeks pregnant. This would be accurate to within 4-5 days each time.


If ultrasound said you were 4.5 weeks pregnant when did you get pregnant?

Around 2.5 weeks ago.


Can an ultrasound tell you exactly how many weeks and days you are pregnant?

It's not an exact science, but it can give you a pretty good idea. the less pregnant you are the more accurate it is. ~pawsalmighty


If the ultrasound shows you to be 26 weeks pregnant is that when you got pregnant 26 weeks ago?

Yes.


Can a ultrasound be accurate if its saying im now due 3 weeks later then they determined?

Can a ultrasound be accurate if its saying im now due 3 weeks later then they determined?


Very irregular menstrual cycle your first day of lmp was aug 28 2005 today on October 13 2006 you are currently 41.5 weeks pregnant according to an us done at 9.2 weeks how accurate was that date?

A baby grows at a very precise rate in the first 12 weeks. A very accurate date can be given as long as you have an ultrasound under 12 weeks. If your ultrasound was at 9.2 weeks, I would consider this accurate.


If you went to the doctor and they did an early ultrasound and said you were 5 weeks and 3 days pregnant could you have an early ultrasound at 3 weeks and 3 days pregnant?

There would be no gestational sac visible @ 3 weeks. YES At 5 weeks 3 days pregnant by ultrasound, you conceived 3 weeks 3 days earlier.


You were 16 weeks pregnant your ultrasound said that the baby size was 18 weeks which one should you do by?

The ultrasound dating has excellent and precise estimation of gestation especially if done in the first trimester (first 12 weeks). After 12 weeks, its accuracy goes down. However, compared to dating according to menstrual cycle, the ultrasound would be more accurate.


When did you conceive if your ultrasound says you are 8 weeks pregnant?

8 weeks ago


When did you conceive if your ultrasound says you are fourteen weeks pregnant?

Subtract fourteen weeks (7 days x 14) from the date of the ultrasound.


Will an ultrasound show heartbeat if you are 6 weeks pregnant?

You could see a heartbeat if they do a transvaginal ultrasound.


Had an ultrasound yesterday. LMP was Nov 2 so you should be 7 weeks The ultrasound only showed you being 5 weeks pregnant you are going back next week for another ultrasound Should you be worried?

You have two due dates...one accourding to your last period and one accourding to the size of the child on the ultrasound...i think the ultrasound one is more accurate


Can your last menstrual period show twenty three weeks but your ultrasound show twenty seven weeks which is more accurate?

ultrasound is more accurate. Measurments of the fetus are made during ultasound that give a more accurate gestational age


How would you know if you were pregnant with twins at eight weeks?

The only sure way of knowing you are pregnant with twins is by ultrasound. An ultrasound at 8 weeks would show if you were carrying a multiple pregnancy.


Can an ultrasound scan be 2 to 3 weeks out The scan says 7 weeks 1 day but could it be that you are actually 10 weeks 1 day pregnant or are they extremely accurate this early?

they a correct withn a couple of days


If someone has an ultrasound and it indicates 7 weeks pregnant from conception date is it possible for the ultrasound to be off by 4 weeks and be 11 weeks pregnant?

No it is not possible to be 11 weeks instead of 7 weeks pregnant. Ultrasound is reliable for dating within a 2 week error. So it is possible for you to be 4 weeks or 9 weeks but not 11 weeks. However dating is usually based on the last menstrual period unless there hasn't been one.


When did you conceive if your ultrasound said you were 8 weeks pregnant on March 19?

Do the math from your last period,and then count up 2 weeks,that should be almost accurate,but all women are differant. And no pregnancy is the same!!!


Why I can't hear my baby heartbeat at 11 weeks pregnant with an ultrasound?

you should be able to....I heard mine on ultrasound at 7 weeks, then at 9 weeks and again last week at 10 weeks! Maybe the person giving you the ultrasound was not experienced enough to do it!


If you were 23 weeks pregnant on your ultrasound and went back 4 weeks later how many weeks should you be?

if you are 23 weeks pregnant , then go back 4 weeks later you should be 27 weeks pregnant. Almost 7 months.


How long after a woman is pregnant can she find out what gender baby she is having?

A woman can have an ultrasound to determine the baby's sex as early as 15 weeks. However, an ultrasound is not 100% accurate - the only way to be 100% accurate is to have an amniocentesis, which is a risky procedure that a doctor won't perform just to determine the baby's sex.


When is a ultrasound done?

Usually a doctor wants to see you for the first ultrasound when you're appr. 10-13 weeks pregnant.