What Is a Chemical Pregnancy?

A chemical pregnancy, also known as a biochemical pregnancy, is a very early miscarriage that occurs when an embryo stops developing before the fifth week of gestation, around the same time as an expected menstrual period. Chemical pregnancies account for between 8% and 33% of pregnancies that end in miscarriage and between 18% and 22% of in vitro fertilization (IVF) pregnancies.

It is not a false pregnancy or a false positive on a pregnancy test, but a pregnancy that occurs before the fetus can be visibly detected on an ultrasound. Chemical pregnancies are often caused by chromosomal abnormalities in the embryo. 

Chemical Pregnancy Symptoms

The majority of people who have had a chemical pregnancy never actually realize they’ve conceived, since the only real symptom is a late period. A chemical pregnancy is sometimes revealed when an early pregnancy test shows a faint positive result but later returns a negative result in a week or two.

Since home pregnancy tests are now quite sensitive, many people find out that they are pregnant very early—even before their expected period. When a chemical pregnancy occurs, the cells of the fertilized egg produce enough of the pregnancy hormone hCG (human chorionic gonadotropin) to elicit a positive pregnancy test result, but then the embryo stops developing.

While you might expect that the menstrual bleeding would be heavier than usual with a chemical pregnancy, it is often the same as a normal period. Other signs of a chemical pregnancy may include:

• Low hCG levels on a blood test
• Mild abdominal cramping or more cramping than usual during a period
• Mild spotting about a week before a normal period is due (this is different than implantation bleeding, or spotting that occurs in early pregnancy)

Because pregnancy hormone levels are present but low in a chemical pregnancy, you wouldn't normally experience any of the other common signs of early pregnancy, such as fatigue or nausea.

While a chemical pregnancy typically doesn't cause any physical harm, it can cause emotional distress. Even the earliest pregnancy loss can lead to feelings of deep sadness and grief.

Chemical Pregnancy Diagnosis

In a chemical pregnancy, the gestational sac will not be large enough to be visible on an ultrasound, so the only way to confirm the pregnancy is through blood tests. (The term "chemical pregnancy" refers to the biochemical means of diagnosis.)

By contrast, a "clinical pregnancy" is one in which either a fetal heartbeat is detected or there is visual evidence on an ultrasound.

Blood pregnancy tests may not be necessary in the case of a chemical pregnancy, but if they are done, they may not be able to detect any hCG or find that levels are falling. In a clinical pregnancy, hCG would be present and rising.

Chemical Pregnancy Causes

While the exact cause of a chemical pregnancy is usually never known, in many cases, they occur because the fertilized egg had some sort of chromosomal abnormality that made it nonviable from the start. Typically, in this case, the fertilized egg will stop developing soon after the egg implants. Or the egg may never implant at all.

Other causes may include:

• Abnormal hormone levels
• Implantation outside the uterus
• Infections (chlamydia or syphilis)
• Uterine abnormalities

Risk Factors

While you can't prevent a chemical pregnancy, there are some known risk factors. Chemical pregnancies are often identified in women who are undergoing IVF. The heightened anticipation of a pregnancy during IVF may lead some couples to test more frequently and earlier than those conceiving naturally.

Other risk factors and untreated conditions that may increase your chances of having a chemical pregnancy include:

• A blood clotting disorder
• Diabetes
• Maternal age over 35
• Polycystic ovary syndrome (PCOS)
• Thyroid disorder

Chemical Pregnancy Treatment

Chemical pregnancies happen early enough that they generally have little effect on a pregnant person’s body and do not require treatment. If one happens, there is also usually nothing barring the couple from trying again immediately.

If you've had more than one chemical pregnancy, however, consult with your doctor to rule out any possible underlying causes and reduce the risk of another early miscarriage.

Grief and Coping

A chemical pregnancy can lead to varying degrees of grieving and loss. Some people may feel little sadness, whereas others may be completely devastated. It is just as ​OK not to feel sad or depressed. Everyone reacts differently to a chemical pregnancy, and there is no single, right response.

As you cope with a chemical pregnancy, keep in mind the following:

• Grief can be isolating. While feelings of sadness and depression are not uncommon, people facing these emotions will often feel isolated in their grief.
• Others may not understand. People may be reluctant to acknowledge the loss and may even suggest that it is unreasonable to feel this way because it wasn’t a "real baby.”
• Your feelings are valid. Regardless of what anyone says, a miscarriage is still a miscarriage. You neither have to justify your grief nor compare it to anyone else’s loss. It is a loss from which you may need time to recover. Give yourself grace and time, and seek support. In addition to reaching out to trusted friends and loved ones, there are many pregnancy loss and support services available.

A Word From Verywell

If you are trying to conceive and are experiencing extreme anxiety (such as can happen in couples undergoing assisted reproduction), some doctors will advise against early pregnancy testing. In order to avoid unnecessary distress, it's wise not to test presumptively or in anticipation of a possible pregnancy, but rather wait until your period is actually late.

It is important to remember that miscarriage from a chemical pregnancy is unavoidable. You can neither stop it nor intervene to prevent it—and it's no one's fault.