Even dating scans can be inaccurate for the due date, but they are never as inaccurate as using the menstrual period. For instance a dating scan done at 6 weeks could get the date wrong five days either way.

Can early dating scans be wrong?

How accurate is the ultrasound examination? The earlier the ultrasound is done, the more accurate it is at estimating the babys due date. Ultrasounds performed during the first 12 weeks of pregnancy are generally within 3 - 5 days of accuracy. The most accurate time is between 8 and 11 weeks gestation.

How inaccurate are dating scans?

Dating from ultrasound scans done later than about 20 weeks is increasingly less accurate. As the chart shows, a scan at 20-28 weeks compared to one at 11-14 weeks resulted in more babies being born apparently “post-term” and more being born apparently premature (22 days or more before the estimated date).

How many days can an ultrasound be off?

Ultrasound dating of conception is not reliable for determining paternity because the test can be off by at least 5-7 days in early pregnancy.

Can a 8 week dating scan be wrong?

An early obstetric ultrasound performed at approximately 8 weeks where a crown rump length (the CRL) is measured precisely predicts an estimated due date accurately. The accuracy of ultrasound measurements used to confirm the calculated due date will be much less accurate further into the pregnancy.

Can my conception date be wrong by 3 weeks?

As pregnancy progresses, the accuracy of an ultrasound for predicting due dates decreases. Between 18 and 28 weeks of gestation, the margin of error increases to plus or minus two weeks. After 28 weeks, the ultrasound may be off by three weeks or more in predicting a due date.

Is it possible for scan not to detect pregnancy?

A pregnancy that doesnt show on an ultrasound scan is called a pregnancy of unknown location. The most common reasons for a pregnancy not appearing on the ultrasound scan are: it is too soon to see the baby on the scan. you have had a miscarriage.