What is a chemical pregnancy and how does it happen?

If you’ve heard a healthcare provider use the term chemical pregnancy, what they’re referring to is a situation where a pregnancy test is positive, but the pregnancy was never actually seen on ultrasound because it ended in miscarriage. 

You may be surprised to learn that over half of all pregnancies actually end this way––often before a woman even finds out she’s pregnant. Here’s everything you need to know about chemical pregnancies, why they happen, and what they mean.

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To understand what a chemical pregnancy really is, it’s important to know a little about timing when it comes to pregnancy in general. If your menstrual cycle is regular, about halfway through the time you finish your last period and start your next an egg is released (a process called ovulation). The egg then travels through a small tube called the fallopian tube and heads towards the uterus.

If it meets sperm along the way, it can be fertilized. This almost always happens in the fallopian tube itself, and usually occurs in the three days after the egg was released. If the egg gets fertilized, it travels towards the uterus where it can implant in the uterine wall and develop into a fetus.

As soon as the fertilized egg implants (and sometimes even before), hormone levels change in the body to preserve and nurture its development. One of those hormones is known as beta HCG.

Even though it will be roughly another two weeks until you miss your period, you’re technically already pregnant. If you were to take a pregnancy test, it may already be positive. That said, a lot of things can go wrong at this stage that causes development to stop. This results in your uterus expelling the fertilized egg and you experiencing a period. About 50% of pregnancies end this way, often before a person even notices they were pregnant.

If you took a pregnancy test and saw it was positive, but the pregnancy ended before you could actually see it on an ultrasound, that’s a chemical pregnancy. It basically means that the chemicals of pregnancy (like HCG) were there. The term miscarriage is more often used to describe a pregnancy that was confirmed by a healthcare provider in a clinical setting using an ultrasound (Chaudhry, 2021).

In grade school, we’re told babies are made when a sperm cell swims upstream and reaches the egg. This step, referred to as fertilization, is just one part of the complex process that is pregnancy.

In the case of a chemical pregnancy, sperm still fertilizes the egg, but the embryo is lost before it has a chance to attach or start developing––usually before your first missed period. The loss can happen before or after implantation (Larsen, 2013).

So what happened? What causes chemical pregnancies to happen? Unfortunately, these types of miscarriages happen so early on it’s hard for experts to determine exactly what happened.

Most specialists agree that abnormal genetic code is a common cause of early miscarriages. Usually, a fertilized egg with irregular chromosomes or cells won’t continue developing, which results in a miscarriage (Dugas, 2021).

Chemical miscarriages are common and often go unnoticed. Many people mistake a chemical pregnancy for a late period. Taking into account many chemical pregnancies happen without anyone knowing, an estimated 50-60% of all pregnancies end before the first missed period  (Annan, 2013, Larsen 2013).

Classic pregnancy symptoms, like morning sickness and fatigue, don’t show up this early. Signs of an early miscarriage may include cramping or vaginal bleeding. For many individuals, it’s difficult to tell the difference between an early miscarriage and normal period symptoms (Dugas, 2021).

With that being said, in order to detect a chemical miscarriage, you first need early pregnancy detection. Early pregnancy detection usually means taking a pregnancy test before typical signs of pregnancy show up, so it’s not that common. Couples undergoing fertility treatment or in vitro fertilization take frequent pregnancy tests and may be more likely to detect a chemical pregnancy.

There is a lot of research investigating if certain hormones or vitamins can prevent miscarriages. Unfortunately, there’s currently no evidence that any particular interventions can change the outcome (Haas, 2019).

Certain risk factors can increase the chance of a miscarriage. These include (Prager 2021):

• Advanced maternal age (being older than 35) 

• A history of miscarriages 

• Medical conditions like diabetes or thyroid problems

• Obesity 

• Stress

• Certain medications or substances

Many of these factors may be out of your control. If you’re actively trying to get pregnant, talk to an obstetrician or fertility specialist who can discuss things like lifestyle changes and what medications are safe to take while pregnant.

If you’ve had a chemical pregnancy, you might wonder what’s next.

Typically, there’s no medical treatment needed after a chemical pregnancy. Your healthcare provider may run some blood tests to make sure your hCG levels are decreasing. This rules out the possibility that the pregnancy has continued somewhere outside of your uterus (like an ectopic pregnancy) (Dugas, 2021).

Many who experience early pregnancy loss experience a range of emotional challenges, including depression, anxiety, and PTSD (Farren 2018). It can be a comfort to know you’re not alone. An estimated one in four women who have been pregnant has a miscarriage by age of 39.

If you’re comfortable, let a provider know how you’re processing the loss––they may be able to offer support or refer you to a specialist. Don’t let a chemical pregnancy stop you from trying to get pregnant again.

In some cases, especially if you experience recurrent chemical pregnancies, a provider may recommend genetic counseling to determine if there are any underlying issues that might be contributing. Speak with your provider about your options: you may be able to start trying again soon after if you feel ready. Having a chemical pregnancy doesn't mean you can't have a healthy pregnancy in the future (Annan, 2013).

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

July 12, 2021

Written by

Hope Chang, PharmD

Fact checked by

Yael Cooperman, MD

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About the medical reviewer

Yael Cooperman, MD, Ro

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.