Expulsion or extraction of the product of conception before 20 weeks of pregnancy or with a weight of less than 500 grams. Threatened miscarriage is the bleeding of the uterine cavity in a pregnant patient. Miscarriage in progress when the cervix is dilated and there are contractions. Incomplete miscarriage involves partial removal of the pregnancy. Complete miscarriage when the product of conception is entirely extracted. Missed miscarriage when no bleeding occurs but there is no heartbeat. Spontaneous miscarriage is when pregnancy loss occurs without any medical intervention. Therapeutic miscarriage is when pregnancy is interrupted by foetal or maternal problems. Biochemical miscarriage is one in which there is pregnancy hormone production (B-HCG) but without the gestational sac forming. Clinical miscarriage is a miscarriage that occurs after or at the same time that it is seen on ultrasound.