A chemical pregnancy is an early pregnancy loss that occurs shortly after implantation. Chemical pregnancies may account for 50 to 75 percent of all miscarriages.
Chemical pregnancies take place before ultrasounds can detect a fetus, but not too early for a pregnancy test to detect levels of BhCG, or beta human chorionic gonadotropin. This is a pregnancy hormone the embryo creates after implantation.
The exact cause of a chemical pregnancy is unknown. But in most cases the miscarriage is due to problems with the embryo, possibly caused by a low quality of sperm or egg.
Other causes may include:
abnormal hormone levels
uterine abnormalities
implantation outside the uterus
Sexually transmitted infections
Being over the age of 35 increases the risk of a chemical pregnancy
blood clotting and thyroid disorder