God distinguishes between deliberate killing and unintended loss, making a clear moral difference between abortion and miscarriage. Abortion is a deliberate act of ending an innocent life, which Scripture condemns (Exodus 20:13), while miscarriage is an unintentional death caused by the brokenness of a fallen world (Genesis 3) and natural circumstances beyond human control (Job; Luke 13:1-5). The Bible affirms that every life, no matter how brief, is valuable to God, and He grieves with those who mourn a miscarriage, offering comfort, hope, and healing (Psalm 139:13-16; Jeremiah 1:5; Psalm 34:18; 2 Corinthians 1:3-4). Miscarriage is not a sin but a consequence of living in a fallen creation where accidents, genetic issues, and natural processes occur. Miscarriage reflects the larger reality of human suffering and the limits of earthly control (Romans 8:20-24). Even in sorrow, God works through grief, demonstrating that His love and purpose remain steadfast, even in the midst of loss.
An abortion is a deliberate action, taken with the specific intent of ending a human life. There is no moral comparison to a miscarriage, any more than there is one between arson and an accidental house fire. It would be ridiculous to excuse an arsonist on the grounds that some houses burn down by accident. Abortion is not made any more moral by referring to miscarriage, any more than murder can be justified by referring to accidental deaths.
Miscarriages occur when something triggers a premature birth. Often, this happens early enough in the pregnancy that the unborn child does not survive. The specific cause of miscarriages vary. They might include an abnormality in the mother's reproductive organs, a disease, hormonal problems, a genetic issue in the child, an illness, or an injury. It may even be due to the negligence or carelessness of the mother or some other person. Miscarriages are unintentional, and this makes all the difference.
God designed the universe to operate under a set of rules and natural laws. He only interferes with the "normal" operation of nature under extraordinary circumstances. The question of why God does not prevent miscarriages is not much different than the question of why God does not prevent any other evil—or all evil, for that matter. This draws in the question of free will and why we are allowed to make certain choices.
Part of the confusion we often have is the assumption that God is doing nothing to restrain evil. Scripture, in fact, suggests the opposite (2 Thessalonians 2:3-7). God has, in fact, limited the extent to which we can suffer in this world (1 Corinthians 10:13). That miscarriages occur doesn't mean God has left the world unchecked. It does, however, mean that we are living in a world of cause and effect, where our choices really do matter.