staying in that position for a long time is particularly bad for a bub, becuase their bones are so soft & still developing, it can cause a lot of problems later in life, as I understand it, it can force the spine into an un natural position. best person to speak to is probably the maternal & child health nurse closest to your home, or a midwife, they will be able to provide you with the relevant literature, or a physio that can explain the long term damage, that you might not connect to an infants sleeping position.