It is thought that approximately 50 - 60% of first trimester miscarriages are due to some type of
chromosomal abnormality. Other causes of
a chemical pregnancy are thought to be related to infection (ie. Chlamydia, Cytomegalovirus, Genital herpes, Syphilis, Toxoplasmosis, and Rubella), abnormal uterine anatomy (ie. unicornate uterus or septate uterus), abnormal hormonal levels within the mother (ie. low progesterone), and systemic illnesses (ie. untreated thyroid disease).