How Accurate Are Baby Due Dates?

Doctors use due dates as a way to ensure that necessary prenatal care is given at the right stages of pregnancy and to measure the baby’s growth. Baby due dates are generally calculated to be 40 weeks after the start of the pregnant woman's last menstrual cycle, based on the assumption that an average cycle lasts for 28 days. But since many women have cycles that differ from the standard 28 days, baby due dates don’t tend to be entirely accurate; it is estimated that just 4% of women give birth on their actual due dates. However, about 60% of women do give birth within a week of their predicted due dates.

More about baby due dates:

  • About 11% of babies are born prematurely, or more than three weeks before their due dates.

  • A woman is more likely to give birth before her due date when it is not her first child; second-born children tend to arrive around three to four days sooner than firstborns.

  • Statistically, the most likely birth date is calculated to be seven days sooner than the actual due date, according to a study of birth information by

Follow wiseGEEK:

More Info: BBC

Discuss this Article

Post your comments

Post Anonymously


forgot password?



Free Widgets for your Site/Blog

As President of Uruguay, José Mujica refused to live in the presidential mansion and gave away 90% of his salary.  more...
October 16 ,  1964 :  China became the fifth country in the world to successfully detonate a nuclear bomb.  more...