Which STIs can cause infertility?

Chlamydia and Gonorrhoea are the main STIs linked to infertility. If they aren’t treated, they can spread from the cervix to the womb, fallopian tubes and ovaries and cause PID. PID can scar the fallopian tubes, which can make it harder to get pregnant and raises the risk of an ectopic pregnancy.

Trichomonas and Mycoplasma genitalium can also cause PID, but a direct link with infertility is less clear. Other STIs, such as Syphilis, Herpes and HIV, affect pregnancy and sexual health in different ways, which we explain below.

PID is an infection of the womb, fallopian tubes and ovaries. The Royal College of Obstetricians and Gynaecologists (RCOG) says about 1 in 4 cases are caused by untreated STIs such as Chlamydia or Gonorrhoea.

Antibiotics usually clear PID, and most women who finish their treatment have no long-term health or fertility problems. Problems are more likely if PID isn’t treated, treatment is delayed or the infection is severe. They include:

• scarring of the fallopian tubes, which can make it harder to get pregnant
• a higher risk of an ectopic pregnancy
• long-term pelvic pain

Repeated episodes of PID raise the risk of fertility problems, so testing and treating STIs early matters. Read more in “What is Pelvic Inflammatory Disease (PID)?”

Chlamydia is the most commonly diagnosed STI in England, and most people who have it don’t get symptoms. UK estimates suggest that 10% to 17% of women with untreated Chlamydia develop PID. Repeated or long-lasting infection can damage the fallopian tubes, and early treatment lowers the risk.

In men, Chlamydia can spread to the epididymis, the tube behind the testicles. The World Health Organization (WHO) says this can lead to infertility in rare cases, and UK guidelines say the link between this kind of infection and fertility is poorly understood. Read more in “Can Chlamydia make you infertile?”

Untreated Gonorrhoea can also cause PID. It causes only a small share of PID in the UK, but in one UK study, about 14% of women with Gonorrhoea had PID.

In men, Gonorrhoea can spread to the testicles or the prostate gland. WHO lists infertility as a possible complication in men, but UK sources don’t say how often this happens. Gonorrhoea in pregnancy can also raise the risk of premature birth and a low birth weight. Read more in “Can STIs cause ectopic pregnancies?”

Trichomonas

Trichomonas is caused by a tiny parasite, not bacteria. The NHS says that if it isn’t treated, it can lead to PID, which can cause infertility. In pregnancy, it can cause a baby to be born early or with a low birth weight.

Mycoplasma genitalium

Mycoplasma genitalium causes about 1 in 10 cases of PID. But UK guidelines say a link with infertility caused by damaged fallopian tubes hasn’t been shown, and they don’t mention any effect on male fertility.

Herpes

UK guidance doesn’t link Herpes to infertility. It matters in pregnancy instead. If you get Herpes for the first time during pregnancy, or have an outbreak when you give birth, your baby could develop a serious illness called neonatal Herpes. Women who had Herpes before pregnancy can usually expect a healthy baby. If you’ve had Herpes, or think you might have it now, tell your midwife.

Syphilis

Syphilis affects pregnancy rather than fertility. It can pass to a baby before birth, which is known as congenital Syphilis, and it raises the risk of miscarriage, premature birth and stillbirth.

HIV

HIV can affect fertility in several ways, but UK guidelines say its overall effect is smaller than once thought, now that treatment works so well. People with HIV on effective treatment with an undetectable viral load can’t pass it on through sex, and UK guidelines recommend sex without a condom to conceive in that situation. People with HIV can have fertility treatment too, if they need it.

The NHS says more than 8 in 10 couples, where the woman is under 40, will conceive naturally within a year if they have regular sex without contraception. See a doctor if you haven’t conceived after a year of trying, or sooner if the woman is 36 or over, or you already know you may have fertility problems.

STIs are only one possible cause of infertility. Other common causes include problems with ovulation and poor-quality semen, and for 1 in 4 couples, no cause is found. Read more in “Can an STI lower my sperm count?”

Better2Know offers:

• Full Screen: tests for 7 infections, including Chlamydia, Gonorrhoea, Mycoplasma, Syphilis and HIV, from 28 days after sex, with results in 3 days (5 days for the home test).
• Platinum Screen: tests for 12 infections, adding Trichomonas, Gardnerella, Herpes 1 and 2 and Hepatitis C to the Full Screen, from 28 days after sex, with results in 3 days.
• Pre-Pregnancy Screen: for women planning a pregnancy. It tests for STIs including Chlamydia, Gonorrhoea, Syphilis, HIV and HPV, and includes a smear test, from 28 days after sex, with results in 5 days, at one of our clinics.

If you’re worried about male fertility, our Sperm Count test checks how many sperm are in a semen sample and how healthy they are. If you test before 45 days, a negative HIV result needs a repeat test. A Syphilis test in the first 3 months after sex can miss the infection, so you may need a repeat test. Not sure which test you need? Our Patient Care Team is available 24/7 on 020 7099 0955.

Can you still get pregnant after Chlamydia?

Yes, in most cases. The risk to fertility comes mainly from PID, especially if it happens more than once, so testing and treating Chlamydia early matters.

Can an STI test show if I’m infertile?

No. An STI test shows whether you have an infection now, not whether an earlier one damaged your fallopian tubes. If you’re having trouble conceiving, see a doctor about fertility tests.

Should I get tested before trying for a baby?

It’s a good idea if you or your partner have had new partners since your last test, as many STIs have no symptoms. Finding and treating an infection early lowers the risk of complications for you and your baby. Read more in “Why you should get a pre-pregnancy STI screening”

Untreated Chlamydia and Gonorrhoea are the STIs most likely to affect fertility, mainly through PID. Both are easy to test for and treat, and most people who are treated promptly have no long-term problems. If you’ve had new partners, a test before you try for a baby gives you peace of mind.

Book a Full Screen at a clinic near you or order a home test kit. Our Patient Care Team is available 24/7 on 020 7099 0955.

Not in the UK? Choose your country from the selector at the top of the page for local tests and prices.

This article originally appeared on 1 September 2023 and was last updated on 1 October 2026.

This article is general information and not a substitute for personal medical advice.

Sources

1. Royal College of Obstetricians and Gynaecologists, Pelvic inflammatory disease, updated January 2026. https://www.rcog.org.uk/for-the-public/browse-our-patient-information/pelvic-inflammatory-disease/
2. NHS, Pelvic inflammatory disease, reviewed 17 December 2025. https://www.nhs.uk/conditions/pelvic-inflammatory-disease-pid/
3. NHS, Infertility, reviewed 9 August 2023. https://www.nhs.uk/conditions/infertility/
4. NHS, Infertility: causes, reviewed 9 August 2023. https://www.nhs.uk/conditions/infertility/causes/
5. NHS, Chlamydia, reviewed 24 October 2024. https://www.nhs.uk/conditions/chlamydia/
6. NHS, Gonorrhoea, reviewed 16 December 2024. https://www.nhs.uk/conditions/gonorrhoea/
7. NHS, Trichomoniasis, reviewed 16 July 2025. https://www.nhs.uk/conditions/trichomoniasis/
8. NHS, Genital herpes, reviewed 27 June 2023. https://www.nhs.uk/conditions/genital-herpes/
9. NHS, Syphilis, reviewed 17 March 2026. https://www.nhs.uk/conditions/syphilis/
10. UK Health Security Agency, NCSP: programme overview, updated 24 June 2021. https://www.gov.uk/government/publications/ncsp-programme-overview/ncsp-programme-overview
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12. British Association for Sexual Health and HIV, UK national guideline for the management of infection with Neisseria gonorrhoeae, 2025. https://www.bashh.org/_userfiles/pages/files/fiferetal2025britishassociationofsexualhealthandhivuknationalguidelineforthemanagementofinfection_1.pdf
13. British Association for Sexual Health and HIV, UK national guideline for the management of pelvic inflammatory disease, 2019 interim update. https://www.bashh.org/_userfiles/pages/files/resources/pidupdate2019.pdf
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15. British Association for Sexual Health and HIV, UK national guideline for the management of epididymo-orchitis, 2020. https://www.bashh.org/_userfiles/pages/files/resources/eo2020.pdf
16. British Association for Sexual Health and HIV and British HIV Association, Guidelines for the sexual and reproductive health of people with HIV, 2026. https://www.bashh.org/_userfiles/pages/files/watersetal2026jointbritishassociationforsexualhealthandhivbritishhivassociationguidelinesforthesexual_1.pdf
17. Human Fertilisation and Embryology Authority, Sperm, egg and embryo donation from people living with HIV with an undetectable viral load, 30 October 2024. https://www.hfea.gov.uk/treatments/hiv/
18. World Health Organization, Chlamydia, 21 November 2025. https://www.who.int/news-room/fact-sheets/detail/chlamydia
19. World Health Organization, Gonorrhoea (Neisseria gonorrhoeae infection), 22 October 2025. https://www.who.int/news-room/fact-sheets/detail/gonorrhoea-(neisseria-gonorrhoeae-infection)
20. World Health Organization, Trichomoniasis, 21 November 2025. https://www.who.int/news-room/fact-sheets/detail/trichomoniasis