Spontaneous abortion is categorized as threatened, inevitable, incomplete, complete, or missed.
Abortion can be categorized further as sporadic or recurrent. By definition, a missed abortion is in utero death of the embryo or fetus before the 20th week of gestation with retained products of conception. Missed abortions also may be referred to as blighted ovum, anembryonic pregnancy, or fetal demise. The timing of a spontaneous abortion suggests its pathophysiology. Anatomic factors usually are associated with second-trimester loss.