Summer infant heart to heart digital prenatal listening system allows you to hear your babys heartbeat the two sets of microphones included in the summer heart to heart prental system allows you to hear the babys movements and heart from approximately 28 weeks its easy to use as it simply straps onto mums tummy and its not invasive it comes complete with an auxiliary lead which can be connected to your computer it is also completely safe and non invasive with no ac current ultrasounds