Spontaneous miscarriage is the loss of fetus before 20 weeks of gestation or delivery of a fetus weighing <500 g, in the absence of elective medical or surgical measures to terminate pregnancy.
Early loss is considered if it occurred before menstrual week 12 while late loss refers to those that occurred from menstrual week 12-20.
It is also known as spontaneous abortion, spontaneous pregnancy loss or early pregnancy failure.