How to accurately calculate the expected date of delivery for pregnant women. The expected date of delivery is the most important date in the minds of pregnant women after pregnancy. However, not everyone knows how to calculate a pregnant woman’s due date. In this article, we will introduce you to four aspects to help you accurately calculate your due date. 1. Basic knowledge of pregnancy period calculation: The pregnancy period is calculated from the first day of the last menstrual period until the day of delivery. The usual pregnancy period is 280 days (40 weeks). If the period is significantly different from the average period, or is irregular, make appropriate adjustments based on the actual situation.