Spontaneous abortion, commonly known as miscarriage, is the natural loss of a pregnancy before 20 weeks of gestation. It can be caused by chromosomal abnormalities, hormonal imbalances, uterine structural issues, infections, or immune factors. Symptoms include vaginal bleeding, cramping, and the passage of tissue. Diagnosis is confirmed through ultrasound and hormone levels (such as hCG). Management depends on the type and timing of the miscarriage and may involve expectant management, medication, or surgical evacuation (D&C).