1. Introduction
The National Center for Health Statistics, the Centers for Disease Control and Prevention, and the World Health Organization define abortion as pregnancy termination prior to
20 weeks of gestation or with a fetus born weighing less than
500 g. The clinical diagnosis of threatened abortion is presumed
when a bloody vaginal discharge or bleeding appears through a
closed cervical os during the first half of pregnancy. These develop in 20–25% of women during early gestation and may persist
for days or weeks. Approximately half of these pregnancies will
abort, although the risk is substantially lower if fetal cardiac
activity is visualized (1).