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How common are false positive syphilis tests in pregnancy?

Pregnant woman sat on floor

Syphilis is a common STD that is caused by the infection of bacteria during sexual activity and can cause a range of problems to your nervous system including headaches, bladder incontinence, meningitis, hearing loss, and visual problems. But were you aware that during pregnancy, false positive syphilis tests are quite common?

In this blog we will discuss how common false positive syphilis tests are during pregnancy, what causes a false positive result, as well as how long it takes to cure syphilis.

How common are false positive syphilis tests in pregnancy?

In order to test for syphilis there are two different types of test; treponemal and nontreponemal.

Treponemal Test :

This tests for antibodies that specifically target T. Pallion,  a bacteria that causes Syphilis. However, despite proving your body is attempting to fight the infection by creating antibodies, this test does not hinder the development of it or reduce the chances of reinfection.

Nontreponemal Test:

This tests for Syphilis in a more direct approach by testing the cardiolipin, which is where the body directs antibodies to.

False positive nontreponemal Syphilis tests can occur in a variety of patients, including those that are pregnant, drug users, have disease that produce similar antibodies, or who have had general virus.

It is now standard practice that if someone receives a positive nontreponemal test result, it must be followed up by a treponemal test to confirm or deny the results.

False positive Syphilis tests are fairly common in pregnancy firstly because it is recommended that every pregnant woman is tested for Syphilis which in itself increases the odds.This is to help prevent the infection spreading to the unborn child which can cause complications including bone damage, anemia, jaundice, liver and spleen complications and in some severe cases death.

However, the main reason why pregnant women tend to receive false positive test results for Syphilis so often is due to any recent acute illnesses as this causes the production of antibodies, fooling the test into thinking they are Syphilis positive. Pregnant women are more exposed to acute illnesses that can pass easily but this can itself interfere with the Syphilis tests.

What could cause a false positive syphilis test?

The main cause for false positive syphilis tests is the production of antibodies that are similar to those that our bodies produce to fight Syphilis. The tests work by identifying said antibodies and translating this recognition as to mean that you are fighting the infection.

Anyone that is recovering from an acute viral illness such as flu is at risk of testing false positive for Syphilis due to the production of antibodies that flu would cause. This is similar for drug users that inject, and pregnant women because they have weaker immune systems and are more exposed to these acute illnesses. .

This is why it is important to be aware of which type of Syphilis test you are taking. If you have tested positive for a Nontreponemal Test it is recommended to follow up with a Treponemal Test to clarify the outcome. This can be done at any private STI testing clinic if you’re looking for peace of mind.

How many penicillin shots does it take to cure syphilis?

The type of treatment required to treat Syphilis depends on how long the patient has been infected. Below are the recommended treatments for Syphilis based on NHS guidance:

If you have been infected for less than 2 years, the recommended amount of penicillin shots is one shot into your buttocks, but alternatively you can take a 10 – 14 day course of antibiotics.

If you have been infected for more than 2 years , the recommended amount of syphilis injections is three shots into your buttocks provided at weekly intervals, or you can take a 28 day course of antibiotics.

For pregnant women the guidelines for treatment after receiving a positive Syphilis STI test is slightly different.

If you are in your first or second trimester of pregnancy and have been infected with Syphilis for less than two years, you can be treated with one penicillin injection into the buttocks. However if you are in your third trimester the recommended amount of injections is two but to be spaced one week apart.

If you have been infected by Syphilis for more than two years the recommended amount of injections is three, split into weekly intervals. However if you are allergic to penicillin you can receive a course of antibiotics to treat the STI instead.

Follow up tests are always recommended after treatment and before engaging in sexual activity again just to make sure the infection has cleared.

How long does it take to cure syphilis?

After your recommended course of Syphilis treatment whether it be penicillin injections or antibiotics, we suggest waiting until you have had a follow up test to confirm you are negative.

Alternatively, you can wait a minimum of 10 days after your course of treatment has finished before engaging in sexual activity but we would recommend getting a private STI test just to be sure.


Get in touch:

If you have noticed a change in your genital area or simply want to test for Syphilis during your pregnancy to be on the safe side, book a private STD test after the incubation period.

Your Sexual Health provides a wide range of STD tests that can be done in clinic or from home to help provide peace of mind as to whether you have been infected by an STD. We also provide a range of Syphilis tests, some of which can provide instant results.


Get in touch with our friendly team today for more information, or if you need advice on which test is right for you.