Miscarriage is the most common complication of pregnancy. It is defined as a pregnancy failure occurring before the completion of 24 weeks of gestation. It has been estimated that 10 to 15% of all pregnancies end in early spontaneous first trimester miscarriage i.e. before the end of the completed twelfth week of pregnancy. The risk of miscarriage decreases with increasing gestational age, and late miscarriages, from 12 to 24 weeks’ gestation, occur in only 1-4% of cases. While miscarriage is rarely associated with significant health problems, it can cause significant psychological distress to the woman and her partner. [With external links to the current evidence base]