11 doctors weighed in:
Do pregnancy dating scans provide accurate results?
11 doctors weighed in

Dr. Kevin O'neil
Obstetrics & Gynecology - Urogynecology
3 doctors agree
In brief: Yes
Early or 1st trimester ultrasound is generally an accurate way to date pregnancy.
However, the further along the pregnancy is, the less accurate the dates.

In brief: Yes
Early or 1st trimester ultrasound is generally an accurate way to date pregnancy.
However, the further along the pregnancy is, the less accurate the dates.
Dr. Kevin O'neil
Dr. Kevin O'neil
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Dr. Patrick Weix
Obstetrics & Gynecology
3 doctors agree
In brief: Yes
Sonograms (ultrasounds) are very accurate, to within a few days, in the first trimester. They are accurate to within about two weeks for the second trimester. They are accurate to within about 3 weeks in the third trimester. Note that your due date will not change once established.
By accurate here, i mean "able to accurately determine gestational age (how far along you are) without knowing lmp.

In brief: Yes
Sonograms (ultrasounds) are very accurate, to within a few days, in the first trimester. They are accurate to within about two weeks for the second trimester. They are accurate to within about 3 weeks in the third trimester. Note that your due date will not change once established.
By accurate here, i mean "able to accurately determine gestational age (how far along you are) without knowing lmp.
Dr. Patrick Weix
Dr. Patrick Weix
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Dr. Craig Keathley
Obstetrics & Gynecology
2 doctors agree
In brief: Yes
Early ultrasound dating by crown-rump length is one of the most reliable pregnancy dating techniques that we have.
That being said- it is not perfect and there is still a margin of error of +/- several days. Pregnancy dating is not an exact science; we frequently refer to pregnancy dating as the "best obstetrical estimate." ultrasounds after the first trimester are less reliable dating tools.

In brief: Yes
Early ultrasound dating by crown-rump length is one of the most reliable pregnancy dating techniques that we have.
That being said- it is not perfect and there is still a margin of error of +/- several days. Pregnancy dating is not an exact science; we frequently refer to pregnancy dating as the "best obstetrical estimate." ultrasounds after the first trimester are less reliable dating tools.
Dr. Craig Keathley
Dr. Craig Keathley
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Dr. David Carcieri
Obstetrics & Gynecology
1 doctor agrees
In brief: Yes
An ultrasound in the first three months of a pregnancy gives the most accurate due date.
As you get further from the first trimester the accuracy decreases. In the third trimester ultrasounds can be as much as three weeks less accurate than a reliable last menstrual period.

In brief: Yes
An ultrasound in the first three months of a pregnancy gives the most accurate due date.
As you get further from the first trimester the accuracy decreases. In the third trimester ultrasounds can be as much as three weeks less accurate than a reliable last menstrual period.
Dr. David Carcieri
Dr. David Carcieri
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Dr. Andrew Silverman
Fertility Medicine
1 doctor agrees
In brief: Yes
Serial sonograms of about 3 weeks apart are extremely accurate for dating especially in the early pregnancy.

In brief: Yes
Serial sonograms of about 3 weeks apart are extremely accurate for dating especially in the early pregnancy.
Dr. Andrew Silverman
Dr. Andrew Silverman
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Dr. Jeff Livingston
Obstetrics & Gynecology
1 doctor agrees
In brief: Yes
Sonograms very accurately measure gestational dates early in the pregnancy.
7 week babies are all roughly the same size so the measurements predicts age well. Later in pregnancy babies growth starts to individualize. It becomes less accurate to predict the gestational age based on their measurements. As a general rule, the earlier the sonogram the more accurate the predicted due date.

In brief: Yes
Sonograms very accurately measure gestational dates early in the pregnancy.
7 week babies are all roughly the same size so the measurements predicts age well. Later in pregnancy babies growth starts to individualize. It becomes less accurate to predict the gestational age based on their measurements. As a general rule, the earlier the sonogram the more accurate the predicted due date.
Dr. Jeff Livingston
Dr. Jeff Livingston
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Dr. Padmavati Garvey
Obstetrics & Gynecology
In brief: Yes
As a general rule, ultrasounds done in the first trimester are accurate to within a week.
Ultrasounds done in the second trimester are accurate to within two weeks. Ultrasounds done in the third trimester can be off by three weeks. So ultrasounds done in the first trimester are very accurate.

In brief: Yes
As a general rule, ultrasounds done in the first trimester are accurate to within a week.
Ultrasounds done in the second trimester are accurate to within two weeks. Ultrasounds done in the third trimester can be off by three weeks. So ultrasounds done in the first trimester are very accurate.
Dr. Padmavati Garvey
Dr. Padmavati Garvey
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