Miscarriage - Spontaneous

Definition

Spontaneous miscarriage, also known as spontaneous abortion, is the unintentional loss of a pregnancy before 20 weeks of gestation, most commonly occurring in the first trimester.

Epidemiology

• Occurs in approximately 10–20% of clinically recognized pregnancies.
• Most common in the first 12 weeks of gestation (first trimester).
• Risk increases with maternal age, especially >35 years.
• Recurrence risk is higher in women with previous miscarriages.

Etiology

• Chromosomal abnormalities in the embryo/fetus (most common cause).
• Maternal factors: uterine anomalies, hormonal imbalances, autoimmune disorders, thrombophilias.
• Infections: TORCH infections, bacterial vaginosis, other systemic infections.
• Lifestyle factors: smoking, alcohol, illicit drug use, obesity.
• Medications: teratogenic drugs or anticoagulants in some cases.

Pathophysiology

• Genetic abnormalities cause embryonic or fetal developmental failure.
• Uterine or cervical structural defects can impair implantation or fetal growth.
• Maternal hormonal deficiencies (progesterone) lead to inadequate support of early pregnancy.
• Immune-mediated mechanisms or infections may trigger trophoblast injury.
• Thrombophilic disorders can lead to placental vascular compromise.