Baby heartbeat Question

Sydney-Marie • I`m 21 years old. I`m married. We have one daughter who we had at 19 year old. We live in a quiet little suburb. I`m a SAHM, and love it to pieces.
At what week can you hear the babies heartbeat thru a vaginal ultrasound? I'm having complications at 7w6d. Going into the ER, but not sure what to expect. Can anyone give me some tips? Please and thank you.