My doctor uses a doppler every visit from about 9 weeks and has never had a problem getting heart beat but having said that i had a checkup at the hospital and the midwife put it on and it took about 3 minutes to find the heart beat. It really depends on the operator. I love hearing the heartbeat but personally wouldn't buy one because i think it would become addictive and possibly a source of further anxiety if i had trouble finding heart beat one time. just my opinion. Some are better than others - like all electronic equipment.