What Is a Chemical Pregnancy?

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A chemical pregnancy occurs when an initial pregnancy test returns a positive result, but it does not progress to a clinical pregnancy.

Also referred to as a biochemical pregnancy, preclinical embryo loss, and trophoblast in regression, a chemical pregnancy is an early pregnancy loss that often occurs just after an embryo implants, at or before five weeks.

Since chemical pregnancies occur at a very early stage, some women may never know they have experienced a chemical pregnancy as they may not have missed a period or taken a pregnancy test. Chemical pregnancies never reach the stage when a gestational sac is viewable in an ultrasound examination.

Positive pregnancy test

Carlos G Lopez / Getty Images 

How Common Is a Chemical Pregnancy?

It is believed the incidence of chemical pregnancy is between 8% to 33% of all pregnancies. For in vitro fertilization (IVF) pregnancies, the incidence is between 18% to 22%.

Causes

The exact cause of chemical pregnancy is unknown.

Some studies suggest a potential cause could be the failure of an embryo to implant due to chromosomal abnormalities.

It is also possible that a chemical pregnancy is due to the uterine lining not being receptive enough to accommodate the implantation of an embryo.

Symptoms

Chemical pregnancy can cause varying symptoms between women, and some women may not notice any symptoms at all. As it happens so early, chemical pregnancy may not cause any symptoms of pregnancy.

Possible symptoms of chemical pregnancy include:

  • Mild abdominal cramping
  • A positive pregnancy test result that can quickly turn negative
  • Minor spotting a week before a due period
  • Bleeding from the vagina even after a positive pregnancy test
  • Low hCG levels in a blood test

Risk Factors

There are known risk factors that may increase the chances of an early pregnancy loss.

Age

Mothers 35 years and older are at an increased risk of pregnancy loss due to the association between maternal age and fetal chromosomal abnormalities.

The impact of paternal age on pregnancy loss is less clear, however some research suggests the risk of early pregnancy loss increases with paternal age.

Medical Conditions

Type 1 and type 2 diabetes can increase the risk of pregnancy loss in the early stages of pregnancy.

Thyroid disease is also associated with an increased risk of pregnancy loss. Both hyperthyroidism and hypothyroidism have this association.

Obesity increases risk of early pregnancy loss. Research suggests a BMI greater than 25 is associated with a 70% increased risk of early pregnancy loss.

Stress

Both chronic and acute stress can increase the risk of pregnancy loss in early pregnancy. Chronic stress can lead to the development of other risk factors for pregnancy loss like increased cortisol levels, increased susceptibility to infection, and decreased immunity.

Substance Use

It is believed smoking, caffeine, and alcohol may increase the risk of pregnancy loss. Exposure to cocaine and methamphetamines may also increase the risk.

Race and Ethnicity

Numerous studies have found an increased risk for early pregnancy loss among Black, Indigenous, and other people of color when compared with White women.

Researchers suggest this increase is indicative of the impact systemic racism can have on health and well-being.

Treatment

No specific treatment is needed for a chemical pregnancy.

Given chemical pregnancy can at times occur unnoticed, many women will not experience any symptoms or notice anything out of the ordinary to warrant treatment.

It is possible some people will experience heavier or more painful bleeding or may pass some small blood clots. Treatment for these symptoms may be needed in some cases.

Some women may worry a chemical pregnancy means their chances of a successful pregnancy later are low. This is not the case. The occurrence of a positive pregnancy test suggests that pregnancy hormones were present and the process of embryo implantation had begun. This means the odds of a healthy pregnancy in the future are better than that of a person who had a negative test. In fact, a chemical pregnancy has no adverse impact on the chance of future pregnancies or future fertility.

A Word From Verywell

Chemical pregnancies can occur even before a woman realizes she is pregnant, and some women may never know if this has occurred. With the improvement of pregnancy tests, more women may learn they have experienced a chemical pregnancy. This may lead to feelings of disappointment and worry.

Having a chemical pregnancy does not lead to adverse outcomes for future pregnancies or fertility. Chemical pregnancies do not require any treatment. If you have concerns, you should speak with your doctor.

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