- Is the unintended termination of pregnancy at any time before the fetus has attained viability (20 weeks gestation or fetal weight of <500g)
- Cause frequently unknown, but 50% are due to chromosomal abnormalities
- Exposure or contact with teratogenic agents
- Poor maternal nutritional status
- Maternal agents with virus such as rubella, cytomegalovirus, active herpes, and toxoplasmosis, or specific bacterial microorganisms that put the pregnancy at risk
- History of diabetes, thyroid disease, anticardiolipin antibodies, or lupus erythematosus
- Smoking or drug abuse of both
- Immunologic factor by which the mother and father are genetically similar, with major antigens that cause the maternal immune system to reject the embryo
- Abnormal uterine development or structural defect in the maternal reproductive system (including an incompetent cervix)
- Environmental factors such as drugs, radiation, or trauma
CLINICAL MANIFESTATIONS
- Uterine cramping
- Low back pain
- Vaginal bleeding usually begins as dark spotting, then progresses to frank bleeding as the embryo separates from the uterus
- B-hCG levels may be elevated for as long as two weeks after loss of the embryo
