A chemical pregnancy is a pregnancy in which the woman tests positive for pregnancy but miscarries before anything can be seen in the uterus on ultrasound. Therefore the only evidence that she was ever pregnant is the chemical reaction that caused the pregnancy test to turn positive. This is also known as a very early miscarriage. In these cases, an egg was fertilized, implanted in the uterus, but then could not continue to grow for some reason. According to ACOG, the American College of Obstetricians and Gynecologists, chemical pregnancies account for 50–75 percent of all miscarriages. Unlike other miscarriages, which typically occur before the 20th week of gestation, chemical pregnancies occur a week or two after implantation. In cases in which the woman is not expecting to become pregnant, she may not even realize she has been pregnant and miscarried, since menstrual bleeding often occurs around the same time. If she is expecting to become pregnant and takes a test, she may get false positive pregnancy test results.
In the past, reliable pregnancy tests could only be performed by doctors. Nowadays, there are several over-the-counter products that can detect pregnancies almost a week before menstruation is due. This could be why more women today realize when they have experienced a chemical pregnancy or early miscarriage. Research has shown up to 70 percent of all conceptions end in miscarriage. Healthcare providers use ultrasound to confirm a clinical pregnancy by finding a sac with a fetus in the uterus. First ultrasounds are typically given between the fourth and sixth weeks of gestation.
Signs and Symptoms of a Chemical Pregnancy
In most cases, women have no symptoms of a chemical pregnancy. In fact, most of these women never even know they were ever pregnant. Some women report mild abdominal cramping and mild spotting a week before their period is due, but there are usually no pregnancy symptoms such as fatigue or nausea, since the pregnancy hormone levels are very low. Blood tests may reveal low hCG levels. Menstrual cycles are typically on time or a week or so late, and may be a little heavier than normal.
What Causes a Chemical Pregnancy?
Experts are unsure what causes a chemical pregnancy, but most believe it happens for the same reasons other miscarriages happen — abnormal chromosomes in the developing embryo. Abnormal chromosomes can be the result of many factors, such as poor quality of the sperm or egg, genetic abnormalities passed down by the mother or father, or an abnormal cell division of the fetus. Experts believe half of all chemical pregnancies are due to some form of chromosomal abnormality. Additional potential causes may include:
- Infections such as toxoplasmosis, chlamydia, or syphilis
- Systemic illnesses such as untreated thyroid disease
- Uterine abnormalities (congenital and acquired)
- Abnormal hormone levels
- Luteal phase defect
- Inadequate uterine lining
- Implantation outside the uterus
Treating and Preventing Chemical Pregnancies
Unfortunately, chemical pregnancies cannot be prevented, nor is there any specific method of treatment. Women who experience a chemical pregnancy are encouraged to follow up with tests to ensure that their hCG levels return to normal, as tubal or ectopic pregnancies can mimic chemical pregnancies.
There is no evidence suggesting chemical pregnancies will affect future pregnancies, and many women who experience chemical pregnancies go on to have healthy pregnancies and deliveries. For some couples, treatment may involve addressing the emotional impact of a chemical pregnancy, especially on those who may be hoping to conceive. Counseling can help you cope with the pregnancy loss. If a couple has had multiple chemical pregnancies, however, they should see their doctor to find out whether there may be a treatable cause. Treatment for recurrent chemical pregnancies may include:
- Progesterone
- Baby aspirin
- Antibiotics (if an infection is present)
- Surgery to fix a uterine abnormality
If you are eager to try to become pregnant again, it is recommended that you wait at least one regular menstrual cycle. Talk with your doctor about an appropriate treatment plan for you.