Hi Bharti, Thanks for discussing your concerns with us. By dates you were 8+3 weeks pregnant on 21st February & your scan showed a 6+1 weeks pregnancy. This happens quite often. There may be a number of reasons e.g. irregular periods, if you were on birth control pills before conceiving, forgotten or wrong dates etc. This may also happen if your sonologist is not experienced enough although mistake is very unlikely in first trimester measurements. Rarely, if you have a missed miscarriage or an empty sac this may also present as a discrepancy. Just make sure that a fetal pole is present & heart beat visible. If this is the case you need not worry. Best of luck.