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.

How accurate are pregnancy due dates?

But data from the Perinatal Institute, a non-profit organisation, shows that an estimated date of delivery is rarely accurate - in fact, a baby is born on its predicted due date just 4% of the time.

Can they be wrong about my due date?

Even once your doctor has established a due date, theres no guarantee that your baby will come that day. In fact, only 6% of women deliver on their due date, Cackovic said. I tell patients that really, your due date is a date in the middle of almost a month-long period of time that you could have your baby.

Can ultrasound due dates be wrong?

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.