Common causes 1. Chromosomal abnormalities: including chromosomal abnormalities in miscarrying couples and chromosomal abnormalities of the villi 2. Anatomical abnormalities: mainly uterine malformations, cervical insufficiency and uterine fibroids 3. Endocrine factors: mainly luteal insufficiency and gestational diabetes 4. Infectious factors. Other causes Immune-related recurrent miscarriage 1. autoimmune type 2. alloimmune type