Ultrasound in Early Pregnancy: Accuracy and Timing

Question
my girl friend is about 7-12 wks pregnant.if we get a ultrasound, will it tells us wene she became pregnant. on which day.and how far along she really is.  

Answer
At 12 weeks gestation (from the first day of her last period) a sonogram is accurate plus or minus 1 week. It can pinpoint exactly how far pregnant she is wihin those parameters. At less than 10 weeks gestation, it is difficult to pinpoint exactly how far she is. I would wait until she is 12 weeks and then get a sonogram. It will tell you when she conceived (plus or minus one week) That is as accurate as it gets. The best indicator of when she conceived is the first day of her last period. If she has a normal 28 day cycle (from the first day of her period until the first day of her next period) ovulation occurs on cycle day #14. She can only become pregnant on cycle day #13, 14, 15, or 16. If she misses her next period and has a positive pregnancy test, you can assume that she conceived on one of thsoe days.