First day of last period Most pregnancies last around 40 weeks (or 38 weeks from conception), so typically the best way to estimate your due date is to count 40 weeks, or 280 days, from the first day of your last menstrual period (LMP).

When do doctors tell you your due date?

Normally, your due date is 280 days (40 weeks or about 10 months -- also known as 10 lunar months) from the first day of your last period.

How early can you find out your due date?

Ultrasound scans can be done at any stage of pregnancy after the first 6 weeks. The best timing for an ultrasound to determine the due date is between 8 weeks and 13 weeks 6 days. You can use the Pregnancy, Birth and Baby due date calculator to work out when your baby is due.

How do doctors determine how far along you are?

To account for the two weeks prior to conception, doctors take the first day of your last menstrual period (LMP) and add 280 days (or forty weeks) to determine the due date. From there, you can also determine how far along you are by counting how many weeks it has been since the first day of your last period.

Do doctors add 2 weeks to your due date?

Thats okay…a few days or even a week of discrepancy wont change your dates. Your doctor will go with the due date obtained from your ultrasound.