The earlier the ultrasound is done, the more accurate it is at estimating the babys due date. Ultrasounds performed during the first 12 weeks of pregnancy are generally within 3 - 5 days of accuracy. The most accurate time is between 8 and 11 weeks gestation.

How do you know what day you conceived?

The best way to determine your conception date is with a pregnancy confirmation ultrasound. Pregnancy ultrasounds look directly at the development of your growing baby to determine its age and when you likely conceived.