Hearing Multiple Heartbeats During Pregnancy: What Could It Mean?

Question
I'm 31 weeks pregnant with mo/di boys. I get weekly US to check fluid levels and dopplers, etc. I have been monitoring heartbeats at home twice a day (not with a medical grade doppler, just one of those "listen to your baby's HB through headphones sort of thing that only picks up a HB if you are right on it) and yesterday the oddest thing happened... I could swear I heard THREE HBs! One low midline and "presenting" one high left and one mid right (my placenta is high right posterior, FWIW and it deffinitely was not my own pulse. I thought I surely must be going crazy so I kept chcking and double checking for over an hour. They would shift around a bit as the babies moved but I was still able to find three different strong HB locations all with different but "normal" heart rates. I tried again this morning and found the same thing.

Could I be going insane? are my multiples multiplying? Is it even remotely possible that I could have a third little one who has been hiding in there all this time? any insight? ever heard of such a thing????

Answer
It's absolutely possible to have a "hidden" multiple.  I remember when we found out about our triplets, the doctors kept not putting "x3!" next to my name on their due date board, and when I asked, they said they were waiting to make sure there weren't any more!!!  I've heard quite a few stories of surprise babies at delivery, too, especially with higher-order multiples.  Another possibility is that you heard an echo.  Heartrates can be variable, and unless you heard them all three at the same time, it's always possible that you counted one twice.  All I can say is ask for an extra check at your next ultrasound.