A due date is an estimate of when your baby will be born. Pregnancy lasts an average of 40 weeks (or 280 days) starting from the first day of your last period (LMP) -But this is an average. The World Health Organization (WHO) defines the natural length of a pregnancy to be 37-42 weeks.
To calculate your due date, you can count 40 weeks on the calendar, or you can subtract 3 months from your LMP and then add 7 days. So for example, if your LMP is 1st January you would subtract 3 months = October 1st+7 days…so your due date is October 8th!
Some providers will change your due date after the first ultrasound. That first-trimester ultrasound is the most accurate for pregnancy dating, even if the LMP is known. It’s generally recommended to change the due date if the ultrasound is done at 9 weeks or less and varies by 5 days or more.
Remember, your due date is just an estimate. Most babies are born within 10 days of their due date, and only about 5% of babies are born on their due date.
So, if due dates are just an estimate, why are they important?
They provide information on approximately how far along you are in your pregnancy. This helps your provider determine:
- When to do genetic testing.
- When to administer labs and blood work.
- Recognize if those results are within the normal range.
- Diagnose pre or post-term pregnancies.
- Track your baby’s growth based on how far along you are.
Image source: Google
