Chemical Pregnancy: What Is It, and What Are the Risks?
It is estimated that about 50-60% of first pregnancies are chemical pregnancies.
Chemical pregnancies, or early miscarriages, happen before five weeks gestation and are very common.
In this condition, the egg has been fertilized, but it doesn't implant into the uterus. These extremely short pregnancies can cause a positive pregnancy test but often go unnoticed and end in the form of late, or even regular, periods.
Chemical pregnancies will never be recognized to be in the uterus on an ultrasound, and therefore are not characterized as clinical pregnancies. It is estimated that about 50-60% of first pregnancies are chemical pregnancies. According to Dr. Amber Cooper, assistant professor in the Division of Reproductive Endocrinology and Infertility at Washington University and a specialist in Reproductive Endocrinology and Infertility at Barnes-Jewish Hospital in St. Louis, chemical pregnancies happen more than one thinks.
“If you take all women who have a positive pregnancy test, 30% will end in a miscarriage, [and] about half of those are chemical pregnancies, meaning they will never be seen on ultrasound,” said Dr. Cooper.
Possible Causes of Chemical Pregnancies
- Low hormone levels
- Luteal-phase defects
- Inadequate uterine lining
- Infection or poor sperm/egg quality
- Genetic abnormalities
It seems most likely that genetic abnormalities are to blame for pregnancies not coming to term. There is not much that can be done to prevent this, but it has been proven that the incidence increases as women age.
“The majority of [chemical pregnancies is] thought to be caused by abnormal chromosomes, most of which spontaneously occur when the early embryo divides,” explained Dr. Cooper.