Can The Fetal Heartbeats Be Detected In The 7th Week Of Pregnancy ?

Hi, My Friend is 7 wk pergnant but still the ultrasound does not detect fetal heartbeat, so her gynac has asked her to wait for 2 weeks more, earlier during 2 weeks back she had spotting as well as 1 day she had clots. Her sonography report removed recently and the one removed 2 week back shows growth of fetua. So is evrthng normal. When is the last that we can expect fetal heartbeats to come. Can anyone wait uptill the 9th week Also I was concerned coz 2 years back i was under the same situation where no heart beats were detected @ the 7week, but also like the above case ther was growth in the fetus, but still the gynac clearly said that it was a case of missed abortion and finally i had to abort in the 8th week for absence of heart beats