Understanding Chemical Pregnancy: What Causes Early Miscarriage?

Medically reviewed by Renita White, MD

A chemical pregnancy occurs when a pregnancy test shows a positive result, but the pregnancy does not progress. A chemical pregnancy results in an early miscarriage just after the embryo implants into the uterine wall. This may occur around five weeks of pregnancy.

It is common to not realize that you experienced a chemical pregnancy. The pregnancy can end before your missed period or positive pregnancy test. A chemical pregnancy does not progress to the stage when a healthcare provider can detect a gestational sac with an ultrasound.

People who are undergoing assisted reproductive technology (ART) may be at a higher than usual risk of experiencing a chemical pregnancy.

This article discusses the causes and symptoms of a chemical pregnancy and when it is safe to try again.

Causes: Why Does Chemical Pregnancy Happen?

Chemical pregnancies are common. It is estimated that up to 25% of pregnancies end before a person knows that they are pregnant.

In most cases, early pregnancy loss is not your fault. It is not caused by everyday activities such as working, exercising, feeling stressed, or having sex. It is often a random event without a known cause.

Chromosomal abnormalities cause most early pregnancy losses. The chromosomes carry genes that tell the cells how to develop. If an embryo has an abnormal number of chromosomes, the risk of early pregnancy loss goes up. 

Timing of Chemical Pregnancy

A chemical pregnancy occurs when an egg is fertilized by sperm, and the embryo begins to implant into the uterine wall. When an embryo implants, high levels of the hormone human chorionic gonadotropin (HCG) can be found in the bloodstream. A pregnancy test can confirm a pregnancy based on the level of HCG in the urine or blood.

In a chemical pregnancy, the pregnancy ends quickly after implantation at about five weeks gestation (five weeks after the last menstrual period).

Chemical Pregnancy and Test Results

Many people who experience a chemical pregnancy never know that they are pregnant because the pregnancy ends before any symptoms begin. High-sensitivity pregnancy tests can detect a chemical pregnancy and will produce a positive result.

Some pregnancy tests can detect a pregnancy three to four days before your missed period. People undergoing in vitro fertilization (IVF) often undergo early pregnancy tests to determine if the embryo transfer was successful. Once the pregnancy ends, a home pregnancy test will produce a negative result.

Related: How Soon Can You Take a Pregnancy Test?

HCG Levels

A pregnancy test detects an early pregnancy by measuring the amount of HCG in the blood. There is a surge of HCG levels once an embryo implants into the uterus. Once a pregnancy ends, HCG levels return to normal levels.

Why Some People Don’t Have Symptoms

Many people do not experience symptoms of a chemical pregnancy because it occurs so early in the pregnancy. A chemical pregnancy cannot be detected with an ultrasound exam.

Possible symptoms of chemical pregnancy include:

• Mild abdominal cramping

• Vaginal bleeding (much like a menstrual period)

• Spotting

Chemical Pregnancy vs. PMS Symptoms

Chemical pregnancy symptoms may feel similar to common premenstrual syndrome (PMS) symptoms. They may also occur around the same time in your cycle.

Common PMS symptoms include:

• Abdominal cramping

• Bloating 

• Tender breasts

• Headache or backache

• Irritability

It can be challenging to determine the cause of the symptoms that you experience before your period. If you believe that you could be pregnant, consider waiting until your missed period before taking a test. 

Chemical Pregnancy Prevention: What’s Uncontrollable

The exact cause of a chemical pregnancy is unknown, so it is often not possible to prevent it.

Because a chemical pregnancy often ends before a missed period, consider waiting to take a pregnancy test until a few days after your missed period. This will prevent you from receiving a positive pregnancy test only to learn that the pregnancy ended shortly after.

People undergoing assisted reproductive technology (ART) may be more likely to experience a chemical pregnancy. It is common for healthcare providers to check your HCG levels shortly after an embryo transfer to determine if the transfer was successful.

ART is intense and can significantly impact your physical and emotional health. This is especially true if you receive a positive pregnancy test only to find out that the pregnancy was a chemical pregnancy. Talk with a healthcare provider about your feelings, and consider meeting with a therapist or support group. 

Coping and Self-Care

There is no right or wrong way to feel after a chemical pregnancy. You may experience feelings of sadness and grief. The physical healing time is relatively quick, but you may need more emotional healing time. Avoid shaming yourself or feeling like it is time to get over it.

If you are concerned about your mood, talk with your healthcare provider. There are therapists and support groups available for people going through ART or early pregnancy loss.

Effect on Future Fertility

Fortunately, a chemical pregnancy does not impact your future fertility. It is possible to become pregnant just two weeks after an early pregnancy loss. You may not feel ready emotionally, so do what is best for you.

When to See a Healthcare Provider

There is usually no treatment needed after a chemical pregnancy. Many people are not aware that they have experienced one. If your menstrual period feels heavier or more painful than usual, consider contacting your healthcare provider. It is also important to talk with your provider if you are concerned about your mood or ability to cope with pregnancy loss.

Summary

A chemical pregnancy occurs when a person has a positive pregnancy test, but the pregnancy does not progress. Many people experience a chemical pregnancy without knowing it. This may be more common in people going through fertility treatments like ART.

A chemical pregnancy results in the loss of an embryo. It often occurs before a person’s missed period, around five weeks' gestation. Many people do not experience symptoms, but possible symptoms include abdominal cramping and vaginal bleeding or spotting.

A chemical pregnancy does not affect your ability to become pregnant in the future. Talk with a healthcare provider about the next steps and when to try again once ready.

Read the original article on Verywell Health.