STIs & genital infections
Chlamydia, HPV, PID and syphilis — impact on fertility, diagnosis and treatment
Last updated: October 2026 — Sources: Cochrane / EAU / ESHRE / WHO / CDC
Key takeaways
STIs are not remote from infertility: chlamydia causes tubal blockage and PID, HPV affects semen parameters, and syphilis in pregnancy threatens the fetus. The difference is that infection is treatable — late diagnosis turns a curable disease into permanent infertility.
Chlamydia is associated with male infertility OR 3.68 (2.24–6.02) — but the case-control design cannot prove causation (Bragazzi 2026).
Seminal HPV lowers motility (SMD −0.82) and normal morphology (−0.52) without changing concentration (Garolla 2024).
CDC 2021 added metronidazole to PID regimens and introduced M. genitalium testing due to macrolide resistance.
Diagnose and treat infection before any fertility intervention — especially with hydrosalpinx or prior PID.
When to evaluate?
- Unexplained infertility or tubal blockage on imaging — test chlamydia and screen for PID.
- Abnormal discharge, dyspareunia or prior PID in the partner — full assessment before IVF.
- Man with unexplained low motility/morphology — seminal HPV testing can be considered after excluding other causes.
What not to do?
- Do not treat one partner alone — infection is shared and reinfection negates treatment.
- Do not rely on serology alone to diagnose current infection.
- Do not start IVF with active hydrosalpinx or untreated PID — outcomes are worse and infection may flare.
Healthcare-professional notice
This hub is independent of NPF products and does not promote them. It is informational only and does not replace individual clinical judgment. Surrogate outcomes (SDF, motility, HOMA, IIEF) are never converted into pregnancy/cure promises, and GRADE certainty is quoted as published.
Binding rule: surrogate outcomes are never converted into patient outcomes. Every certainty grade and limitation is quoted as published.
Deep dive
From infection to tubal blockage
Chlamydia infects tubal epithelium and is often silent; chronic inflammation leads to fibrosis, adhesions and fimbrial blockage.
The resulting hydrosalpinx prevents implantation via fluid reflux and inflammatory mediators — hence discussion of salpingectomy or occlusion before IVF.
Impact on men
Epididymal/testicular infection raises ROS and DNA damage, appearing as low motility and morphology — without necessarily meaning complete infertility.
Exogenous testosterone is not relevant here; the effect is local inflammation, and early treatment prevents permanent fibrosis.
Evidence in this domain
Each study broken into five questions: why it was run, who was studied, how it was done, the finding, and why it came out that way — then the clinical takeaway and limits, as published.
FAQ
Does treating chlamydia restore fertility?
Treatment stops infection and prevents further damage, but fibrosis from prior inflammation does not reverse — timing matters.
Notice: this reference is informational only and not a substitute for medical advice. Consult your doctor before making any treatment decision.