How accurate are doctors with due dates?
More than 90% are born two weeks either side of the predicted date.
But, as noted above, only 4% (or 4.4%, ignoring pregnancies with complications etc) are born on the predicted date itself – in other words, the chance of this happening is less than one in 20..
How often do doctors change your due date?
Your doctor may change your due date based on the ultrasound measurement. This is most likely to occur in the first trimester, especially if the date estimated by the ultrasound differs by more than one week from the date estimated by your doctor based on your LMP.
Why do doctors add 2 weeks to pregnancy?
That was the moment of conception. By the time most women miss a period and find out they’re pregnant, the baby has been growing for 2 weeks, but the mother is actually 4 weeks along because the gestational period starts with the first day of your last period.
Is conception date or last period more accurate?
Because few women know the exact day they ovulated or conceived, an ultrasound done in the first trimester of pregnancy has been shown to the be the most accurate way to date a pregnancy. If an ultrasound date in the first trimester differs from your LMP date by seven days or more, we would go with the ultrasound.
Can conception date be off by 2 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.
How common is it for due date to be wrong?
The chance of delivering exactly on your magically assigned date is rare — only 5% of women will deliver on their Estimated Due Date. So there’s a pretty good chance that your due date is wrong too.