I am pregnant and due to a previous ectopic, I have had 4 ultrasounds so far and I am 24 weeks along. When first asked by my practioner the first day of my last period, I explained that the "last" period in Feb. was extremely abnormal and very different from my normal periods. Not only was it almost 1 week early (although I am always off a few days) but the flow was very light and sort of on and off if you will. I remember wondering if everything was okay. Then, I did not have a period in March and later found out I was pregnant. Anyway, my practioner counted that Feb. period as the last period I had. Every untrasound that I have had has my due date around Nov. 20th. I can only assume that it really was a "real" period in Feb. and I conceived during ovulation later in the month of Feb. My question is how accurate are the unltrasounds. What are the chances that I am actually futher along, meaning I conceived during ovulation in January? I would hate to go into labor when I am not expecting it at all. Can I rest assure that I am due around Nov. 20th based on the ultrasounds that I have had? Are the ultrasound dates calculated freely or is information entered based on the last period? I am wondering what their accuracy is. I just cannot forget how different that "last" period was and I am worried because my doctor is using that one as a normal one. Thanks!