Between 18 and 28 weeks of gestation, the margin of error increases to plus or minus two weeks.
The most common misconception we encounter almost daily, has to do with how accurate ultrasounds are in fixing the EDC at different stages of pregnancy.
Both these situations are considered largely avoidable.
In our practice, the EDC will be determined at the first prenatal visit whenever possible, and subsequent ultrasounds, which often will report a different (often earlier) EDC will not override the first EDC.
Naturally, one of the most common questions asked about ultrasound accuracy is: Just how accurate are the due dates that are predicted by an ultrasound?
Evidence suggests that, in the first 20 weeks of pregnancy, the first ultrasound may be the most accurate tool for predicting when your baby will be born.