1. Pregnancy
  2. Pregnancy health
  3. Miscarriage

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Chemical Pregnancy: Symptoms, Causes, and Preventing Miscarriage

What is a chemical pregnancy? It’s a term for a common early pregnancy loss that happens soon after implantation. Let’s take a closer look at chemical pregnancy, its causes, and whether it can be prevented.

What is a chemical pregnancy?

A chemical pregnancy is also known as biochemical pregnancy or biochemical loss. It is the medical definition given to an early and spontaneous abortion or very early miscarriage. It’s a normal pregnancy, in that conception happens after ovulation, the embryo implants, and a pregnancy test confirms the pregnancy. However, a miscarriage happens before the embryo or fetus can be seen in the uterus. 

Some people who experience a chemical pregnancy never knew they were pregnant. 

A chemical pregnancy is confirmed when an early pregnancy test reveals a positive result but later returns a negative result in a week or two. Sometimes the only real sign or symptom is a late period.

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How common are chemical pregnancies?

Early miscarriages are quite common. The chance of a miscarriage is between 8 and 20 percent before 20 weeks of pregnancy, and 80 percent of early miscarriages occur before 12 weeks. 

Chemical pregnancies may account for 25–50 percent of all miscarriages in cases when a person had no signs and didn’t know they were pregnant. Biochemical pregnancy may occur in 20 percent of pregnancies from assisted reproductive technologies.

The main risk factors for chemical pregnancy are maternal age and previous miscarriages. At 20–30 years old, the possibilities of experiencing a miscarriage can range from 9 to 17 percent; this increases with age.

Chemical pregnancy symptoms

Chemical pregnancies often go unnoticed. Sometimes, they may present with the following symptoms: 

  • Bleeding with or without clots. In 20–30 percent of all pregnancies, there is some bleeding in early pregnancy, with about 50 percent of those not ending with a miscarriage.
  • Uterine pain and cramping

Causes of chemical pregnancies

Chemical pregnancies happen when an egg becomes fertilized but the implantation isn’t completed. A combination of random factors can lead to miscarriage, and sometimes it is difficult to find one cause. 

Potential causes of chemical pregnancies include:

  • Chromosomal abnormality. About half of cases occur when there is an abnormal number of chromosomes. 
  • Infections such as chlamydia or syphilis
  • Uterine abnormalities 
  • Systemic ailment such as untreated thyroid disease or uncontrolled diabetes
  • Abnormality in hormone levels (luteal phase defect)
  • Low body mass index 
  • Smoking and alcohol increase the risk of miscarriage

Chemical pregnancy or implantation bleeding: What’s the difference?

Bleeding from a miscarriage (chemical pregnancy)

In general, bleeding associated with a chemical pregnancy may start as light spotting and then turn to excessive bleeding with visible clotting (dark red clots), similar to a heavy period. Cramping and heavier bleeding are other signs of a chemical miscarriage.

Bleeding from implantation bleeding

In contrast, implantation bleeding appears as a light-brown discharge with a lighter flow that will last only a few hours to a few days. Vaginal bleeding happens in a very small amount around 10–14 days after conception, around the time of the next expected period. The bleeding occurs when the fertilized egg implants itself in the uterine wall.

How long does chemical pregnancy bleeding last?

Chemical pregnancy is different from other miscarriages. One person early in the pregnancy may have a miscarriage and only experience bleeding and cramping for a few hours. Another person may have miscarriage bleeding for up to a few days, and it may look like menstrual bleeding. This is why chemical pregnancies often go unrecognized.

How to prevent chemical pregnancy

Since most miscarriages happen because of random abnormalities in chromosomes, there is nothing specific that can be done to prevent them. Maintaining a healthy lifestyle is a good way to maintain a healthy pregnancy, though. Monitoring health and preparing for a pregnancy before conceiving can help support a healthy pregnancy. Here are a few steps to practice good pre-pregnancy health:

  • Regular exercise
  • A healthy diet
  • Stress management
  • Maintaining a healthy weight
  • Eating iron-rich food and taking folic acid every day
  • Avoiding smoking and alcohol
  • Сontrolling and managing existing medical conditions (e.g., diabetes, thyroid issues, and blood diseases)
“Miscarriage.” Mayo Clinic, MFMER, Accessed July 16, 2019, https://www.mayoclinic.org/diseases-conditions/pregnancy-loss-miscarriage/symptoms-causes/syc-20354298

Chaudhry K, Tafti D, Siccardi MA."Anembryonic Pregnancy", NCBI, StatPearls Publishing Treasure Island (FL), Accessed Aug 10,2020, https://www.ncbi.nlm.nih.gov/books/NBK499938/

Togas Tulandi. “Patient education: Miscarriage (Beyond the Basics).” UpToDate, Accessed Oct 09, 2019, https://www.uptodate.com/contents/miscarriage-beyond-the-basics/print

“Early Pregnancy Loss” The American College of Obstetricians and Gynecologists, FAQ090,Accessed February 2020, https://www.acog.org/womens-health/faqs/early-pregnancy-loss

Yvonne Butler Tobah “Implantation Bleeding: Normal in Early Pregnancy?” Mayo Clinic, Mayo Foundation for Medical Education and Research, 9 May 2019, www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/expert-answers/implantation-bleeding/faq-20058257.

Clark Alves,Amanda Rapp. “Spontaneous Abortion” NCBI, Bookshelf, Accessed July 20, 2020, https://www.ncbi.nlm.nih.gov/books/NBK560521/

Zanetti, Bianca Ferrarini et al. “Predictive factors for biochemical pregnancy in intracytoplasmic sperm injection cycles.” Reproductive biology vol. 19,1 (2019): 55-60. doi:10.1016/j.repbio.2019.01.004

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