This paper describes the motivation and process of developing a musical instrument for an unborn child. Well established research shows a fetus in the womb can respond to and benefit from stimuli from the outside world. A musical instrument designed for this unique context can leverage the power of this interaction. Two prototypes were constructed and tested during separate pregnancies and the experiences are presented, and the limitation of the sensor technology identified. We discuss our discoveries about design considerations and challenges for such an instrument, and project thought-provoking questions that arise from its potential applications.