Is It Normal To Have A Fetal Heartbeat At 7.3 Weeks Of Pregnancy?

hi my wife missed periond on 7 sept 2011 and we made the pregnancy test after 45 day it showed negative and we also did the blood beta hcg test it also showed negative we went to our gynacolgist with the report she preferd meprate for 5 day but the period dint come once again itoke her to the gynecologist she gave us dupheston 5 tab still the period dint come yesterday we when to another clinic and the scaned and told me my wife is 7 weeks and 3 day pregnate they also showed me the heart beat of the fetous it was also normal will these tablet affect my baby