Heartbeat hears a heartbeat!

Before we knew William was a William, we called the baby Heartbeat. When we went for our first ultrasound for him, the sound of his tiny heart was so amazing that Mommy teared up and Daddy nearly fainted. Last week, Mommy went to the doctor for a check-up, and William was able to come along to hear the new baby's heartbeat. It was a shwoosh-shwoosh sound. The doctor told him it was baby baseball, to which William responded in an incredulous tone "baby baseball?" I think William thought the doctor was a little crazy. How could a baby heartbeat be baseball?