Brief description of miscarriage Spontaneous termination of a fetus weighing less than 1000g at less than 28 weeks of gestation is known as spontaneous miscarriage, with an incidence of about 15%-40%. There are two types of miscarriage: spontaneous and induced. Spontaneous abortions are mostly early abortions, and 50%-60% are related to embryonic chromosomes. Spontaneous abortion occurs in 31% of embryos after implantation, of which 80% are early abortions. Among early miscarriages, about 2/3 of occult miscarriages, i.e. miscarriages that occur before menstruation, are also called biochemical pregnancies. 1.Early miscarriage: before 12 weeks. 2.Late miscarriage: before 12-28 weeks Causes of miscarriage Embryonic factors, maternal factors, paternal factors, environmental factors. 1.Early miscarriage: embryonic chromosomal abnormalities, endocrine abnormalities, reproductive immune disorders and pre-thrombotic state. 2.Late miscarriage: and embryo stop development is mostly seen in pre-thrombotic state, infection, etc. Those with fresh embryos mostly have uterine malformation, cervical insufficiency and other anatomical factors.