That study, conducted by the National Institute of Environmental Health Sciences, has similarly shown that just about 4 percent of women give birth on their due date, while 70 percent have their baby within 10 days of the predicted arrival.

Is it common to get a due date wrong?

It is very common when scanning an early pregnancy to find that the due date does not match the menstrual history. Sometimes the dates can be more than a week off and sometimes even as much as 4 weeks.