Can I get a positive pregnancy test and not be pregnant?

The truth is, getting pregnant isn’t always that easy and for many couples, it can be a very confusing time. Sometimes, it’s possible to have a positive pregnancy test, even when you aren’t pregnant! This is known as a false-positive and the reason lies in the bHCG hormone. Dr Irafna Koita, a consultant fertility specialist with more than 15 years of experience, explains a bit more about this hormone and why it can give you an incorrect result.

What is the beta HCG hormone?

Beta human chorionic gonadotropin (bHCG) is a hormone, commonly referred to as the pregnancy hormone. The hormone is produced in the placenta after fertilisation and nourishes the egg during the complete period of pregnancy.

The levels of this hormone are first detected by a blood test (known as the beta HCG test) 11 days after conception and after 12-14 days by a urine test. The beta HCG levels can vary significantly between individuals and from one pregnancy to the next, however, bHCG levels typically follow a range throughout a healthy pregnancy.

It’s regular for bHCG levels to double every 72 hours and peak in the first 8-11 weeks of pregnancy. During the later stages of pregnancy however, these levels begin to drop. If high levels of bHCG are detected, it means that the pregnancy is developing normally. Although, when bHCG levels do not increase or decrease as they should, this may be a sign of a problem. It’s important to remember, however, that low bHCG levels are not always a sign that something is wrong.

What can cause low levels of bHCG in blood?

Miscalculated gestational age

Gestational age describes how far along the patient is in their pregnancy. An estimated birth-date is calculated based on the last menstrual period, therefore if the patient has a history of irregular periods or they are unsure of their last menstrual period before getting pregnant, then the gestational age may be misjudged. As a result, low bHCG levels are then indicated.

Ectopic pregnancy

This happens when the embryo attaches outside the uterus, usually inside the fallopian tube (the tube that takes the egg from the ovary to the uterus). As well as having low bHCG levels, women may experience abdominal pain and vaginal bleeding.

Blighted ovum

A blighted ovum occurs when a fertilised egg attaches to the uterus but fails to develop into an embryo. It can also be referred to as an anembryonic pregnancy. It can occur during early pregnancy, sometimes before a person even knows they are pregnant. Currently, it is the leading cause of miscarriage or early pregnancy failure. Ultrasound and repeat bHCG levels may be needed to help correlate bHCG levels and gestational age.

Miscarriage

A miscarriage is a loss of pregnancy during the first 20 weeks of pregnancy. Levels of bHCG may rise initially in these situations but fail to increase or decrease as they should afterward.

Can we prevent or treat low bHCG levels?

There is currently no way to prevent low bHCG levels or these associated complications. There is, however, treatment available for the underlying conditions that cause low bHCG levels. Even if a complication associated with low bHCG levels occurs, such as a miscarriage or an ectopic pregnancy, this does not mean that someone will be unable to get pregnant again or that their fertility is compromised. A successful pregnancy is still possible with low bHCG levels.

Can you get a positive pregnancy test and not be pregnant?

It is important to remember that the bHCG hormone is chemically very similar to that of LH (Luteinizing hormone) which is produced by the pituitary gland and is one of the main hormones that control the reproductive system. While pregnancy tests can tell the difference between LH and bHCG, ovulation tests cannot. As a result, when you take an ovulation test and you have bHCG levels that are above an LH test’s detection sensitivity for LH, it will display a positive result because it will detect high levels of the bHCG hormone. This similarity can explain how false-positive pregnancy results can happen.

There are other causes of false-positives. Very rarely, if you are using a home pregnancy test and you have blood or protein in your urine, it can show up as a positive result. Some types of drugs, such as hypnotics and fertility drugs, can also cause this.

If you have any problems with infertility or you need to speak to a specialist about any of the conditions mentioned in this article, visit Dr Irfana Koita's Top Doctors profile and book an appointment with her today.