how to calulate due date of pregnancy

[mommychula02]

I started what I thought was my period 2/7/2013 an ended the next night. Then I found out on the 20th that I was pregnant. Does that little periid count to caluclate my due date???

[Number3onherway]

if your unsure your doctor can give you an estimated due date based on ultrasound mesaurements of the fetus. i had alot of bleeding when i was 6 and 9 weeks prego. im now 33 weeks. if your sure of your last period you just add 7 days then add 9 months and thats your due date! my period was august 12 2012 my due date is may 19 2013

[nae_moore]

I'm thinking that may have actually been your implantation bleeding. You may have to go by the first day of you previous cycle. I'm pretty sure you would have gotten a negative preg test on the 20th otherwise cuz you wouldnt have been far enough along for it to detect