This is a channeled message from Spirit.
There can be different reasons, the soul chooses to stay only for a short time to experience the process of being born and in a physical body. Or perhaps they are born into a body,
or family that was different than they thought it would be. Still others may want their family to grow in whatever way is best for them. Perhaps bringing parents together, help a mother open her heart, or open a doorway for her journey in life. It is not to bring pain and sorrow to be held by the mother for a lifetime, but as snapshot of that time in her life. However, the mother goes on from there is her journey and perhaps she will know after her grief is gone, or much later in life it will be revealed to her. The time spent with the mother may be brief but forever held in her heart.