ordinarymom

The part about "assuming" that you ovulate at 14 days after your period is right. My early ultrasounds were the most accurate for both of my sons. Later I had an ultrasound that pushed my due date up by 3 weeks because my baby was big! My first was 9 1/2 pounds and 23" long. I went into labor on my due date and had him 9 minutes after midnight on the next morning. 4 days is not a big difference. Could be a bigger baby. Unless you know for certain the exact date you conceived, those due dates could be a little off. That's probably why we hear 2 weeks before or after your due date is considered full term.