Due Date

Due date is the date a pregnant woman is expected to give birth. This date is an important indicator for tracking the progress of pregnancy and for medical management and preparation. Due date is usually calculated in the following way:

• Calculation from the first day of the last menstrual periodThe most common method is to add 280 days (about 40 weeks) from the first day of the last menstrual period. This is because pregnancy is calculated based on a normal menstrual cycle (about 28 days) and the day of ovulation. This method is called the "Nägele method."
• Calculation from the date of sexual intercourseIf fertilization is considered to have occurred on the day of sexual intercourse, 266 days are added from that day to calculate the due date. This method is applicable when the date of fertilization can be identified.
• Confirmation by ultrasound examinationAn ultrasound examination performed early in pregnancy can measure the size of the fetus and more accurately determine the number of weeks of pregnancy. It is common to revise the due date based on the results of this measurement.

The due date is only a guideline, and the actual date of delivery often varies. Most pregnant women give birth within 1 to 2 weeks of the due date.

• Due date = start date of last menstruation + 280 days (40 weeks)
• Due date = date of sexual intercourse + 266 days (38 weeks)

1. Enter the "start of your last menstrual period" or the "date of sexual intercourse". Either one is fine.
2. The "due date" will be calculated automatically.

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