Definition, Signs and Causes of a Chemical Pregnancy

Woman re-examining her pregnancy test

A chemical pregnancy is a very early pregnancy loss, usually occurring during the first 3 ½ to 5 weeks of your pregnancy. It is a real pregnancy. The term 'chemical' is used because the pregnancy can only be detected by a urine or blood test (chemistry) and cannot be seen on an ultrasound. A chemical pregnancy doesn't make it beyond the first few cellular stages of development.

What Are the Signs of a Chemical Pregnancy?

With a chemical pregnancy, a blood or urine test first shows that you are pregnant, but later the test becomes negative. Women who don't do an early pregnancy test and have no symptoms of early pregnancy will often never know they had a chemical pregnancy loss.

Bleeding may occur at the time of the expected next period or a few days later. Sometimes this bleeding is a bit heavier or longer than normal.

How Does Your Doctor Make The Diagnosis?

If your pregnancy is normal, the chemical or hormone of pregnancy, Human Chorionic Gonadotropin (HCG), rises normally in an expected way. In a chemical pregnancy your first HCG level is often lower than expected and does not rise normally. Urine and blood pregnancy tests can now detect HCG early, before your next period is due.

Your doctor uses one of three ways to make the diagnosis of a chemical pregnancy:

  • The HCG in your blood test does not increase as expected on repeat testing.
  • The HCG decreases on repeat testing.
  • Your home pregnancy test or urine test at your doctor's office is positive but your follow-up blood test is negative.

Repeating your blood HCG about every 2 days, usually until it is negative, is the standard way to confirm that you have a chemical pregnancy. Your doctor can also choose to order an ultrasound to evaluate inside your uterus.

Is a Chemical Pregnancy Loss a Miscarriage?

A miscarriage is any pregnancy loss up to 20 weeks from the last normal period. A chemical pregnancy loss, though in the very early cellular stages before a fetal sac or a fetus develops, is a miscarriage. Some doctors, however, do not label chemical pregnancy as a miscarriage because the loss is so early.

How Often Does a Chemical Pregnancy Occur?

According to the National Institutes of Health (NIH), about 15-20 % of known pregnancies (diagnosed by a positive pregnancy test) are lost before the 20th week of pregnancy. Most pregnancy losses happen very early before 12 weeks of pregnancy. After 12 weeks the risk becomes less and less as the pregnancy progresses.

If you include chemical pregnancies, the rate of pregnancy loss is even higher. The true percentage of chemical pregnancies is not known because most of these pregnancies go unrecognized. It is now more common to detect them, however, because more women are doing an early pregnancy test before they miss their next period. This is even more so if you undergo in vitro fertilization (IVF) treatment because pregnancy testing is routinely done early.

What Are the Causes of a Chemical Pregnancy?

The majority of chemical pregnancy losses or miscarriages happen because of abnormal chromosomes in the embryo. This is caused by poor sperm or, more often, poor egg quality, or by abnormal genes in the man or woman. Abnormal chromosomes are more likely the earlier the pregnancy is lost. The remaining early losses includes failure of the embryo to implant normally in the uterine lining. This may occur for a variety of reasons, including:

  • The progesterone hormone did not increase enough after ovulation to prepare the lining for implantation.
  • The lining did not thicken normally although the progesterone level was normal.
  • There are abnormalities in the lining such as a fibroid tumor, scar tissue or a dividing septum that interfere with the embryo attaching itself to the lining.

Whether you have a chemical pregnancy or a later miscarriage your doctor will also consider the following causes:

  • Infections such as Chlamydia, herpes, toxoplasmosis, or syphilis
  • Chronic illnesses such as diabetes, high blood pressure or lupus
  • Immune factors in the mother that attack the embryo or fetus
  • Hormone imbalances such as thyroid disease
  • Poor nutrition and vitamin deficiencies such as folic acid
  • Abuse of alcohol, tobacco or drugs

How to Deal With a Chemical Pregnancy

The loss of a baby at any stage, chemical or later, can be devastating. Your doctor, midwife, or nurse will offer support and advice. Ask a lot of questions so you can understand your individual situation. Try to get the emotional support that you need from your partner, family or friends.

Don't be afraid to try again but don't try to get pregnant right after your bleeding stops. Best to wait till after at least one normal period to give you time to recover from the emotional impact. Your doctor might want you to wait even longer to evaluate and treat any conditions that might increase your chances of another pregnancy loss.

Chemical pregnancies occur often, though many women might be unaware that they had one. If it happens to you, rest assured that you most likely will go on to have normal pregnancies and babies. Follow your doctor's advice about what to do, when to get further testing, and when it is ok to get pregnant again.

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Definition, Signs and Causes of a Chemical Pregnancy