This document provides an overview of abortion in 3 parts: definitions, classifications, and clinical presentation. Abortion is defined as the termination of a pregnancy before 22 weeks or when the fetus weighs less than 500g, according to the WHO. Abortions can be spontaneous, induced, or therapeutic. Clinically, threatened abortion presents with vaginal bleeding and is diagnosed by ultrasound. Complete abortion involves passage of pregnancy tissues. Complications include hemorrhage and infection.