What are some things that can cause miscarriages besides stress?

Many things possible: Any woman may have a miscarriage, as a normal part of life. If a woman has recurrent miscarriages, there are some known causes (other than bad luck) such as genetic disorders (like a chromosomal abnormality), autoimmune causes (like anti-phospholipid syndrome), anatomic causes (such as a malformed uterus), and environmental causes (like smoking).