Miscarriage is the spontaneous loss of a pregnancy before 20 weeks of gestation and occurs in up to 20% of pregnancies, most often during the first trimester. Common symptoms include vaginal bleeding, abdominal cramping, lower back pain, and a sudden reduction in pregnancy-related symptoms. These signs require prompt medical evaluation. Miscarriages are most commonly caused by chromosomal abnormalities but may also result from hormonal imbalances, underlying maternal health conditions, or lifestyle factors such as smoking and substance use. Routine activities like stress or exercise are not typical causes.