If it was an old machine and things were blurry, are they certain it was even a second baby? One of my pregnancies my early office ultrasound showed two "babies" but when I had a better scan at the hospital the same day baby #2 turned out to be the yolk sac. With RJ we could see the heartbeat at 5w5d plain as day on a basic machine (abdominally and transvag). At 5w3d with Brighton on the basic machine we could see what appeared to be an occasional flicker so they confirmed on the good machine that it was the heartbeat they saw, super early because it was only 68 bpm at that point and a bit irregular. They say the heartbeat becomes visible early in the 6th week on average, which was why I asked if they were sure it was a second baby. I know occasionally they have a hard time visualizing a heartbeat though. But if they could take measurements off a fetal pole I'd expect they'd be able to find it by now. I wouldn't worry so much and just wait for the next scan to see what's going on.
<blockquote><b>Quoting Spackgirrl:</b>" UPDATE: Had the appt this afternoon for a better ultrasound and happy to say there is just one healthy ... [snip!] ... high tech ultrasound at 2pm and should know more then. Can you see a heartbeat at 6 weeks 3days-ish? Please be honest. Thanks"</blockquote>