What is a Chemical Pregnancy? Why does it Happen?

by Aug 7, 2019

What is a chemical pregnancy?

It can be devastating to see a period after a positive pregnancy test result, but it is actually more common than you might think. You may have experienced what your doctors called a chemical pregnancy or biochemical pregnancy, which is an early pregnancy loss happening shortly after implantation. Chemical pregnancies may account for up to 70% of all miscarriages. It is considered a type of miscarriage.


Many women who ever had a chemical pregnancy actually never found out they were pregnant. The only real sign they may have noticed is the late monthly period.

Chemical pregnancy takes place before the fetus can be detected by ultrasounds. But a pregnancy hormone called human chorionic gonadotropin or hCG can be detected in the blood or urine already. Your doctor confirms your pregnancy with a blood test of hCG. Your home pregnancy test measures the level of hCG in urine.

What happens during a chemical pregnancy?

One week after ovulation, the fertilized egg implants itself onto the uterus lining. It starts to produce levels of pregnancy hormone hCG.

However, for some reason, the implantation never fully developed, and ultrasound can’t detect the gestational sac. Bleeding often happens about a week after your expected period if you have 28-day cycles. You may want to see your doctor right away if you experience heavy bleeding after a false-positive pregnancy test.

What are the symptoms of chemical pregnancy?

Most women can experience no symptoms.

Some women can have menstruation-like cramps and vaginal bleeding about a week after the positive pregnancy test. Chemical pregnancy shouldn’t lead to nausea or fatigue as a normal pregnancy does.

It is important to note the difference between bleeding after chemical pregnancy and implantation bleeding. When the embryo attaches to the uterus lining, this process could damage the small vessels on the uterus wall. Implantation bleeding is often called implantation spotting. It is usually brown or pink in color and happens about 9 days after ovulation. It can range between 6-12 days.

Different from other early miscarriages, chemical pregnancy occurs shortly after implantation.

What causes a chemical pregnancy?

When an egg and sperm meet each other, they combine their chromosomes and form a fertilized egg, which rapidly divides and grows.

Sometimes mistakes happen during this process. The egg and sperm produce too many or too few chromosomes. These chromosomal abnormalities are believed to be the root cause of early pregnancy losses. It can randomly happen to anyone.

Age is one of the major risk factors of early pregnancy loss, especially if you are over 35 years old. As women age, these eggs are also more likely to have chromosomal abnormalities. This means there are some small mistakes within their DNA. The chance of a chemical pregnancy is also higher.

Other causes may include abnormal hormone levels, uterine abnormalities, ectopic pregnancy, inadequate uterine lining, low body mass index, and other infections.

How long does chemical pregnancy bleeding last?

Some women in their early pregnancy may only bleed for a few hours after a miscarriage occurs. Others may bleed and cramp up to a week.

Do you need to see a doctor after a chemical pregnancy?

Very early pregnancy losses usually don’t require medical intervention. If you have symptoms of fatigue, tiredness, dizziness, nausea, or heavy vaginal bleeding, you should see a doctor immediately to rule out the risk of ectopic pregnancy.

Usually, one or two chemical pregnancies should not indicate serious underlying problems. The good news is you don’t have to wait three months after a pregnancy loss to try to conceive again.

A study has actually shown a very short interpregnancy interval of fewer than three months has no detrimental effects on pregnancy outcomes. There is little difference in terms of live birth rate, another miscarriage, and pregnancy complications. However, if you have reproductive medical conditions before the pregnancy, or your symptoms last longer than usual, you should talk with your doctor and medical treatment might be necessary.

What will my cycle look like after a chemical pregnancy?

Your cycle after a chemical pregnancy will just look like any other cycle. You should ovulate at the usual time.

What can you do after a chemical pregnancy?

The most important treatment after an early miscarriage is to prevent infection and hemorrhaging. It usually requires no further medical treatment because the earlier the loss happens, the more likely your body can expel all the fetal cells out of the body. Infection and excessive bleeding can occur if your body is unable to do so.

Because most of the early miscarriages happen due to chromosomal abnormalities, there is not much can be done to prevent them. Our eggs age with us. This means there are small mistakes in their DNA. Once the mistakes happen, there is no way to reverse them back. Abnormal DNA can lead to cells not functioning correctly and in the case of an egg, it may not make for optimal fetal health development.

Specifically, 90% of eggs are genetically normal in early 20s. <20% of eggs remain healthy by mid 40s. So if you are beyond age 35, talk to your doctor after a chemical pregnancy.

You will also want to find the best timing. Once you ovulated, the egg only lives up to 12-24 hours within a woman’s fertile mucus. When trying to conceive, it is important to find the first few hours after ovulation to increase the chance of a healthy pregnancy. You will want to track your ovulation precisely using a product like Mira, which tells your actual hormone concentrations and hormone curve, so you will not miss the peak fertility window.

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Another vital step to prevent early pregnancy loss is a healthy lifestyle. Closely monitor and work on your health before pregnancy takes place. Proper exercise, healthy food, stress management, weight monitoring, and avoiding smoking and drinking are proven to be helpful. You should also consider prenatal vitamins such as folic acid and iron supplements.

✔️ Medically Reviewed by Banafsheh Kashani, MD, FACOG

Banafsheh Kashani, MD, FACOGBanafsheh Kashani, M.D., FACOG is a board-certified OB/GYN and specialist in reproductive endocrinology and infertility at Eden Fertility Centers, and has been treatingcouples and individuals with infertility since 2014.

Dr. Kashani has conducted extensive research in female reproduction, with a specific focus on the endometrium and implantation.

Additionally, Dr. Kashani has authored papers in the areas of fertility preservation, and fertility in women with PCOS and Turners syndrome. She also was part of a large SART-CORS study evaluating the trend in frozen embryo transfers and success rates.

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