A miscarriage is the unintended death of an unborn baby, also referred to as a spontaneous abortion.
I don’t believe a miscarriage is a sin (though it is a consequence of living in a sinful, fallen world). It is not a procured abortion. There is no intent on the part of the mother to terminate her pregnancy. She wants to have the baby but for whatever reason her body is unable to carry the child.
Miscarriage is suffering, not sin.
[Answered by Dr. Stephen Tu, Trinity Pacific Church, Vancouver, Canada]