Incomplete miscarriage

Miscarriage is the most common complication of pregnancy. It is defined as the loss of pregnancy before 24 weeks. Underlying causes and risk factors of miscarriage include fetal abnormality (50%), infection ('TORCH'), increasing maternal age, maternal illness (diabetes, renal disease), abnormal uterine cavity (intrauterine contraceptive device insertion, congenital septum), antiphospholipid syndrome and intervention (amniocentesis and chorionic villus sampling). Note that exercise, intercourse and emotional trauma do not cause miscarriage. Investigation into the underlying cause of miscarriage is performed only if three miscarriages have occured.

In incomplete miscarriage, some of the fetal material has passed, but some products of conception are retained in the uterus (these are visible on ultrasound scanning). The cervical os remains open until all the products have passed (whether that be spontanous, or with medical or surgical assistance). A complete miscarriage is when the mother has experienced bleeding, all the fetal tissue has passed, there are no products of conception on scanning and the cervical os is closed. In these cases, patients do not require further hospital follow-up.

A threatened miscarriage is when there is bleeding before 24 weeks, but the fetus is still alive and the cervical os is closed on examination. Only 25% of threatened miscarriages eventually miscarry.

An inevitable miscarriage describes a scenario where there is bleeding before 24 weeks and the cervical os is dilated. The fetus may still be alive but the miscarriage will occur.

Finally, a missed miscarriaged (also known as a delayed or silent miscarriage) is when the fetus dies in utero and the cervix stays closed. There may or may not be bleeding in this case.