Understanding Pregnancy Due Dates

A pregnancy due date is an estimated date, not a guarantee. It helps healthcare providers track pregnancy progress, schedule prenatal care, and estimate fetal development milestones. Many pregnancies deliver before or after the estimated due date.

How due dates are commonly estimated

One common method counts about 40 weeks from the first day of the last menstrual period. This method assumes typical cycle timing, so it can be less accurate for people with irregular cycles or uncertain dates.

Why ultrasound may change the date

Early ultrasound measurements may help estimate gestational age. If measurements do not match the last menstrual period estimate, a healthcare provider may update the due date.

How to use a due date estimate

• Use it to understand your pregnancy timeline.
• Bring it to prenatal appointments.
• Ask your provider if ultrasound dating changes the estimate.
• Do not use an online calculator as a replacement for medical care.

Try our pregnancy due date calculator to estimate your timeline.