I have just spent 2 hrs looking for babies HB convincing myself of all sorts... I eventually found the LO but realized why I couldnt pick up the HB. They are so sensitive that the louder your heart races the less chance you have of picking it up. I was in a right panic, couldnt find baby anywhere, I was tossing and turning to try make baby move into another position but nothing- LO was obviously near the placenta and was also hiding near one of the areas in my body that has a pulse running near it- ie: groin area- the closer to the groin, the louder my pulse and the doppler just couldnt pick up the baby. It was in the background but the LCD screen was only registering mine so I had no indication of where little en was.. I must say, it absolutely terrified me I will definitely not be checking as often anymore...it causes panic.