Refused to let us hear the heart beat??

Not sure how I'm feeling after today's very first visit at my ob office. I found out I was pregnant February 26th and scheduled my appointment that same day.... After waiting for what seemed like FOREVER, today was the day and I was looking forward to it. I had my ultrasound and everything looked fine and we saw the heart beating (164) and everything, but she refused to let us hear the heart beat! I was so confused and she said they don't do any "audio" until after 12 weeks. Has anyone heard this?? My dr said it's because that particular piece of equipment can cause the fetus to "warm up", increasing the risk for miscarriage or defects. Dont get me wrong, I'm glad that our baby looked healthy, but just not hearing the heart beat was disappointing. :(